Cephalotaxus esters, methods of synthesis, and uses thereof

ABSTRACT

The present invention provides novel cephalotaxus esters, syntheses thereof, and intermediates thereto. The invention also provides pharmaceutical compositions comprising a compound of the present invention and methods of using said compounds or compositions in the treatment of proliferative diseases (e.g., benign neoplasm, cancer, inflammatory disease, autoimmune disease, diabetic retinopathy) and infectious disease. The invention further provides methods of using said compounds or compositions in the treatment of multidrug resistant cancer.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of and claim priority under 35U.S.C. § 120 to U.S. application, U.S.S.N. 12/920,227, filed Dec. 8,2010, which is a national stage filing under 35 U.S.C. § 371 ofinternational PCT application, PCT/US2009/035868, filed Mar. 3, 2009,which claims priority under 35 U.S.C. § 119(e) to U.S. provisionalapplication, U.S.S.N. 61/033,187, filed Mar. 3, 2008, the contents ofeach of which are incorporated herein by reference.

GOVERNMENT SUPPORT

This invention was made with United States government support undergrant GM67659 awarded by the National Institutes of Health—NationalInstitute of General Medical Sciences, and a predoctoral fellowshipawarded by the National Science Foundation. The United States governmenthas certain rights in the invention.

FIELD OF THE INVENTION

The present invention relates to cephalotaxus esters, syntheses thereof,and intermediates thereto. The invention also provides pharmaceuticalcompositions comprising compounds of the present invention and methodsof using said compounds or compositions in the treatment ofproliferative diseases (e.g., benign neoplasm, cancer, inflammatorydisease, autoimmune disease, diabetic retinopathy) and infectiousdisease.

BACKGROUND OF THE INVENTION

Cephalotaxus harringtonia, commonly known as the Japanese plum-yew, is asmall evergreen shrub native to Eastern Asia. Alcoholic extracts of thepowdered leaves and stems of Cephalotaxus genera yielded cephalotaxineas the most abundant alkaloid constituent (L. Huang and Z. Xue,Alkaloids 1984, 23, 157-226; W. W. Paudler, J. McKay and G. I. Kerley,J. Org. Chem. 1963, 28, 2194). While cephalotaxine accounts forapproximately 50% of the mass of the crude alkaloid extract mixture,several minor constituents have also been identified. Among these areseveral rare C3-ester derivatives (K. L. Mikolajczak, C. R. Smith and R.G. Powell, Tetrahedron 1972, 28, 1995; R. G. Powell, D. Weisleder, C. R.Smith, Jr. and W. K. Rohwedder, Tetrahedron Lett. 1970, 815-818; I.Takano, I. Yasuda, M. Nishijima, Y. Hitotsuyanagi, K. Takeya and H.Itokawa, J. Nat. Prod. 1996, 59, 965-967; D. Z. Wang, G. E. Ma and R. S.Xu, Acta pharmaceutica Sinica 1992, 27, 173-177).

The cytotoxic properties of the cephalotaxus esters arise fromreversible inhibition of protein synthesis (M. T. Huang, Mol. Pharmacol.1975, 11, 511-519) via induction of rapid breakdown of the polyribosome,with concomitant release of the polypeptide chain (M. Fresno, A. Jimenezand D. Vazquez, Eur. J. Biochem. 1977, 72, 323-330). The remarkableanti-leukemia activity of several Cephalotaxus esters spawned intenseinvestigations into their therapeutic potential. Several Cephalotaxusesters demonstrate acute toxicity toward various murine leukemia, murinelymphoma, and human epidermoid carcinoma cells (H. Morita, M. Arisaka,N. Yoshida and J. Kobayashi, Tetrahedron 2000, 56, 2929-2934; Powell, etal., supra). Homoharringtonine (HHT) has advanced through clinicalstudies and is now used for the treatment of chronic myeloid leukemia.However, difficulties in production, hematologic toxicity, andsusceptibility to multidrug resistance (MDR) have hindered its clinicaldevelopment (Z. Benderra, H. Morjani, A. Trussardi and M. Manfait,Leukemia 1998, 12, 1539-1544).

Cephalotaxine itself has been found to be biologically inactive (M. A.J. Miah, T. Hudlicky and J. W. Reed, Alkaloids 1998, 51, 199-269),highlighting the necessity for an elaborate C3 ester side chain foranticancer activity. However, the naturally occurring ester derivativesare typically attainable in only <0.1% of the plant dry weight. Whilecertain cephalotaxus ester derivatives, namely HHT, are availablethrough semisynthetic methods, such approaches are not appropriate forother bioactive members of the family. A versatile and streamlinedsynthetic approach will allow for the chemical synthesis of virtuallyany cephalotaxus ester, and will enable cytotoxic profile evaluation ofcephalotaxine derivatives in efforts to combat multidrug resistance.

SUMMARY OF THE INVENTION

The present invention encompasses the recognition thathomoharringtonine, the clinically favored cephalotaxus ester, is highlysusceptible to multidrug resistance (MDR), thus inherently limiting itstherapeutic potential. Novel non-natural cephalotaxus ester compoundsare provided that are cytotoxic against both hematological and solidtumor cell lines.

In one aspect, the invention provides compounds of formula I:

or a pharmaceutically acceptable salt thereof, wherein:

-   each    independently designates a single or double bond;-   R¹ is hydrogen, optionally substituted C₁₋₆ aliphatic,    —(CH₂)_(n)CO₂R⁸, —(CH₂)_(n)CON(R⁸)₂, —(CH₂)_(n)COSR⁸, or taken    together with R² to form an optionally substituted, saturated or    unsaturated 3-7-membered ring having 0-2 heteroatoms independently    selected from nitrogen, oxygen, or sulfur; and    -   each R⁸ is independently hydrogen, an optionally substituted        group selected from cephalotaxine, C₁₋₆ aliphatic, 6-10-membered        aryl, or C₁₋₆ heteroaliphatic having 1-2 heteroatoms        independently selected from nitrogen, oxygen, or sulfur;    -   n is an integer from 0-4;-   R² is hydrogen, —NR₂, —OR, or an optionally substituted group    selected from acyl, C₁₋₆ aliphatic, or C₁₋₆ heteroaliphatic having    1-2 heteroatoms independently selected from nitrogen, oxygen, or    sulfur;-   R³ is -T-R^(z), wherein:    -   T is a covalent bond or a bivalent C₁₋₁₂ saturated or        unsaturated, straight or branched, hydrocarbon chain, wherein        one or two methylene units of T are optionally and independently        replaced by —O—, —S—, —N(R)—, —C(O)—, —C(O)O—, —OC(O)—,        —N(R)C(O)—, —C(O)N(R)—, —S(O), —S(O)₂—, —N(R)SO₂—, or —SO₂N(R)—;        and    -   R^(z) is hydrogen, halogen, a monosaccharide, a disaccharide,        —OR, —SR, —NR₂, —N₃, or an optionally substituted group selected        from acyl, arylalkyl, heteroarylalkyl, C₁₋₆ aliphatic,        6-10-membered aryl, 5-10-membered heteroaryl having 1-4        heteroatoms independently selected from nitrogen, oxygen, or        sulfur, 4-7-membered heterocyclyl having 1-2 heteroatoms        independently selected from nitrogen, oxygen or sulfur; or        -   a hydrogen radical on R^(z) is replaced with a substituent            of the formula:

-   -   wherein each occurrence of R¹, R², R⁴, R⁵, R⁶, R⁷, T, and R^(z)        may be the same or different;

-   R⁴ is hydrogen, —OR, or ═O;

-   R⁵ and R⁶ are each independently selected from hydrogen, C₁₋₆    aliphatic, —SO₂R, —CO₂R; or R⁵ and R⁶ are taken together with their    intervening atoms to form an optionally substituted 5-7-membered    ring having 0-2 heteroatoms independently selected from nitrogen,    oxygen, or sulfur;

-   R⁷ is hydrogen, —OR, —OCO₂R, —OCOR, —OCOSR, or —OCONR₂; and

-   each R is independently hydrogen, an optionally substituted group    selected from acyl, arylalkyl, C₁₋₆ aliphatic, or C₁₋₆    heteroaliphatic having 1-2 heteroatoms independently selected from    nitrogen, oxygen, or sulfur; or:    -   two R on the same nitrogen atom are taken with the nitrogen to        form a 4-7-membered heterocyclic ring having 1-2 heteroatoms        independently selected from nitrogen, oxygen, or sulfur.

According to one aspect, inventive compounds have been shown to beuseful as antiproliferative agents against multiple cancer cell lines,including those of hematopoietic malignancies, acute promyelocyticleukemia, T cell leukemia, acute lymphoblastic leukemia, Mantle celllymphoma, B cell lymphoma, acute lymphoblastic T cell leukemia,neuroblastoma, adenocarcinoma, Ewing's sarcoma, glioblastoma, epithelialcarcinoma, cervical adenocarcinoma, or well-differentiated liposarcomacancers, to name but a few. In certain embodiments, compounds of formulaI are useful against cancer cell lines that are multidrug resistant. Insome embodiments, the cells are HL-60/RV+ cells. In some embodiments,the cells are resistant to homoharringtonine. In some embodiments,compounds of formula I are useful for treating cancer in a subjectsuffering therefrom. In certain embodiments, compounds of formula I areuseful for treating refractory cancers in a subject suffering therefrom.In some embodiments, compounds of formula I are useful for treatingdrug-resistant cancers in a subject suffering therefrom.

In another aspect, the invention provides pharmaceutical compositionscomprising compounds of the invention and pharmaceutically acceptableexcipients.

In another aspect, the invention provides kits comprising pharmaceuticalcompositions of inventive compounds. In some embodiments, the kitscomprise prescribing information. In some embodiments, such kits includethe combination of an inventive compound and another chemotherapeuticagent. The agents may be packaged separately or together. The kitoptionally includes instructions for prescribing the medication. Incertain embodiments, the kit includes multiple doses of each agent. Thekit may include sufficient quantities of each component to treat asubject for a week, two weeks, three weeks, four weeks, or multiplemonths. In certain embodiments, the kit includes one cycle ofchemotherapy. In certain embodiments, the kit includes multiple cyclesof chemotherapy.

In another aspect, the invention provides a method of treatinginfectious disease in a subject comprising administering to the subjecta therapeutically effective amount of an inventive compound. In someembodiments, the subject is human. In certain embodiments, the infectionis caused by a bacterium. In certain embodiments, the infection iscaused by a fungus. In certain embodiments, the infection is caused by aparasite.

In yet another aspect, the invention provides a method for synthesizingcephalotaxus ester derivatives through a cross metathesis strategy, themethod comprising the steps of:

-   (a) providing a compound of formula A:

wherein:

-   R¹ is hydrogen, optionally substituted C₁₋₆ aliphatic,    —(CH₂)_(n)CO₂R⁸, —(CH₂)_(n)CON(R⁸)₂, —(CH₂)_(n)COSR⁸, or taken    together with R² to form an optionally substituted, saturated or    unsaturated 3-7-membered ring having 0-2 heteroatoms independently    selected from nitrogen, oxygen, or sulfur; and    -   each R⁸ is independently hydrogen, an optionally substituted        group selected from cephalotaxine, C₁₋₆ aliphatic or C₁₋₆        heteroaliphatic having 1-2 heteroatoms independently selected        from nitrogen, oxygen, or sulfur;    -   n is an integer from 0-4;-   R² is hydrogen, —NR₂, —OR, or an optionally substituted group    selected from acyl, C₁₋₆ aliphatic, or C₁₋₆ heteroaliphatic having    1-2 heteroatoms independently selected from nitrogen, oxygen, or    sulfur;-   T is a covalent bond or a bivalent C₁₋₁₂ saturated or unsaturated,    straight or branched, hydrocarbon chain, wherein one or two    methylene units of T are optionally and independently replaced by    —O—, —S—, —N(R)—, —C(O)—, —C(O)O—, —OC(O)—, —N(R)C(O)—, —C(O)N(R)—,    —S(O), —S(O)₂—, —N(R)SO₂—, or —SO₂N(R)—;-   PG³ is a suitable protecting group; and-   each R is independently hydrogen, an optionally substituted group    selected from acyl, arylalkyl, C₁₋₆ aliphatic, or C₁₋₆    heteroaliphatic having 1-2 heteroatoms independently selected from    nitrogen, oxygen, or sulfur; or:    -   two R on the same nitrogen atom are taken with the nitrogen to        form a 4-7-membered heterocyclic ring having 1-2 heteroatoms        independently selected from nitrogen, oxygen, or sulfur;        and-   (b) treating said compound of formula A under suitable conditions    with a compound of formula B:

wherein:

-   R^(y) is hydrogen, halogen, a monosaccharide, a disaccharide, —OR,    —SR, —NR₂, —N₃, or an optionally substituted group selected from    acyl, arylalkyl, heteroarylalkyl, C₁₋₆ aliphatic, 6-10-membered    aryl, 5-10-membered heteroaryl having 1-4 heteroatoms independently    selected from nitrogen, oxygen, or sulfur, 4-7-membered heterocyclyl    having 1-2 heteroatoms independently selected from nitrogen, oxygen,    or sulfur;    in the presence a suitable cross metathesis catalyst, to form a    compound of formula C:

In certain embodiments, a suitable cross metathesis catalyst is Grubbs2^(nd) generation catalyst.

The invention further provides compounds of formulae III-A, III-B,III-C, or III-D:

or a pharmaceutically acceptable salt thereof, wherein:

-   each    independently designates a single or double bond;-   R¹ is hydrogen, optionally substituted C₁₋₆ aliphatic,    —(CH₂)_(n)CO₂R⁸, —(CH₂)_(n)CON(R⁸)₂, —(CH₂)_(n)COSR⁸, or taken    together with R² to form an optionally substituted, saturated or    unsaturated 3-7-membered ring having 0-2 heteroatoms independently    selected from nitrogen, oxygen, or sulfur; and    -   each R⁸ is independently hydrogen, an optionally substituted        group selected from cephalotaxine, C₁₋₆ aliphatic, 6-10-membered        aryl, or C₁₋₆ heteroaliphatic having 1-2 heteroatoms        independently selected from nitrogen, oxygen, or sulfur;    -   n is an integer from 0-4;-   R² is hydrogen, —NR₂, —OR, or an optionally substituted group    selected from acyl, C₁₋₆ aliphatic, or C₁₋₆ heteroaliphatic having    1-2 heteroatoms independently selected from nitrogen, oxygen, or    sulfur;-   R³ is -T-R^(z), wherein:    -   T is a covalent bond or a bivalent C₁₋₁₂ saturated or        unsaturated, straight or branched, hydrocarbon chain, wherein        one or two methylene units of T are optionally and independently        replaced by —O—, —S—, —N(R)—, —C(O)—, —C(O)O—, —OC(O)—,        —N(R)C(O)—, —C(O)N(R)—, —S(O), —S(O)₂—, —N(R)SO₂—, or —SO₂N(R)—;        and    -   R^(z) is hydrogen, halogen, a monosaccharide, a disaccharide,        —OR, —SR, —NR₂, —N₃, or an optionally substituted group selected        from acyl, arylalkyl, heteroarylalkyl, C₁₋₆ aliphatic,        6-10-membered aryl, 5-10-membered heteroaryl having 1-4        heteroatoms independently selected from nitrogen, oxygen, or        sulfur, 4-7-membered heterocyclyl having 1-2 heteroatoms        independently selected from nitrogen, oxygen or sulfur; or        -   a hydrogen radical on IV is replaced with a substituent of            the formula:

-   -   wherein each occurrence of R¹, R², R⁴, R⁵, R⁶, R⁷, T, X, and        R^(z) may be the same or different;

-   R⁴ is hydrogen, —OR, or ═O;

-   R⁵ and R⁶ are each independently selected from hydrogen, C₁₋₆    aliphatic, —SO₂R, —CO₂R; or R⁵ and R⁶ are taken together with their    intervening atoms to form an optionally substituted 5-7-membered    ring having 0-2 heteroatoms independently selected from nitrogen,    oxygen, or sulfur;

-   R⁷ is hydrogen, —OR, —OCO₂R, —OCOR, —OCOSR, or —OCONR₂; and

-   each R is independently hydrogen, an optionally substituted group    selected from acyl, arylalkyl, C₁₋₆ aliphatic, or C₁₋₆    heteroaliphatic having 1-2 heteroatoms independently selected from    nitrogen, oxygen, or sulfur; or:    -   two R on the same nitrogen atom are taken with the nitrogen to        form a 4-7-membered heterocyclic ring having 1-2 heteroatoms        independently selected from nitrogen, oxygen, or sulfur;

-   R″ is hydrogen or an optionally substituted group selected from    acyl, arylalkyl, C₁₋₆ aliphatic, or C₁₋₆ heteroaliphatic having 1-2    heteroatoms independently selected from nitrogen, oxygen, or sulfur;    and

-   X is a suitable counter ion.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 depicts the chemical structures of cephalotaxine and relatedesters.

FIG. 2 depicts selected non-natural cephalotaxus esters of formula I.

FIGS. 3 and 4 show comparative antitumor effects of cephalotaxus estersagainst sensitive and vincristine-resistant HL-60 cells.

FIG. 5 depicts the correlation of calculated log P values and MDRresistance ratio for selected cephalotaxus esters.

FIG. 6 depicts a retrosynthetic analysis and summary of key steps in thesynthesis of cephalotaxus esters.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

Cephalotaxine has received considerable and enduring attention in thearena of total synthesis. Several syntheses of cephalotaxine have beenreported over the past three decades. The significance of the complexcephalotaxus esters (e.g., deoxyharringtonine, homoharringtonine,homodeoxyharringtonine, and anhydroharringtonine, see FIG. 1) extendsbeyond that of cephalotaxine on several levels, the most prominent ofwhich being their exceedingly potent anti-proliferative properties.Moreover, the scarcity of these complex ester derivatives from thenatural source is far more pronounced than that of cephalotaxine,wherein complex cephalotaxus esters are typically attainable in only<0.1% of the plant dry weight. Thus, in one aspect the inventiondescribed herein provides a novel synthetic approach to bioactivecephalotaxus esters that is markedly different from prior approaches.

In another aspect, the invention described herein enables extensivecytotoxicity evaluation of several advanced natural and non-naturalcompounds with an array of well established human hematopoietic andsolid tumor cell lines. In certain embodiments, the inventive compoundsare cytotoxic. In some embodiments, the inventive compounds arecytotoxic when tested against these cell lines. Structure-activityrelationships based on these natural and non-natural cephalotaxus esterssuggests modifications to modulate multidrug resistant (MDR) cancersusceptibility. In some embodiments, those modifications include ahydrogen bond donating group at the C2′ position of the ester sidechain. In certain embodiments, the lipophilicity of the ester side chainis correlated with low susceptibility to MDR. In some embodiments, theplacement of more lipophilic groups at the C6′ position of the esterside chain, relative to that of homoharringtonine, is correlated withlow susceptibility to MDR.

In certain embodiments, potent cytotoxicity is observed in several celllines previously not challenged with these alkaloids. In someembodiments, comparative cytotoxicity assays reveal the potential ofsynthetic structural modification of this family of alkaloids tomodulate susceptibility to multi-drug resistance.

Compounds

Compounds of this invention include those described generally above, andare further illustrated by the classes, subclasses, and speciesdisclosed herein. For purposes of this invention, the chemical elementsare identified in accordance with the Periodic Table of the Elements,CAS version, Handbook of Chemistry and Physics, 75^(th) Ed.Additionally, general principles of organic chemistry are described inOrganic Chemistry, Thomas Sorrell, University Science Books, Sausalito:1999, and March's Advanced Organic Chemistry, 5^(th) Ed., Ed.: Smith, M.B. and March, J., John Wiley & Sons, New York: 2001, the entire contentsof which are hereby incorporated by reference.

Description of Exemplary Compounds

In certain embodiments, the present invention provides a compound offormula I:

or a pharmaceutically acceptable salt thereof, wherein:

-   each    independently designates a single or double bond;-   R¹ is hydrogen, optionally substituted C₁₋₆ aliphatic,    —(CH₂)_(n)CO₂R⁸, —(CH₂)_(n)CON(R⁸)₂, —(CH₂)_(n)COSR⁸, or taken    together with R² to form an optionally substituted, saturated or    unsaturated 3-7-membered ring having 0-2 heteroatoms independently    selected from nitrogen, oxygen, or sulfur; and    -   each R⁸ is independently hydrogen, an optionally substituted        group selected from cephalotaxine, C₁₋₆ aliphatic, 6-10-membered        aryl, or C₁₋₆ heteroaliphatic having 1-2 heteroatoms        independently selected from nitrogen, oxygen, or sulfur;    -   n is an integer from 0-4;-   R² is hydrogen, —NR₂, —OR, or an optionally substituted group    selected from acyl, C₁₋₆ aliphatic, or C₁₋₆ heteroaliphatic having    1-2 heteroatoms independently selected from nitrogen, oxygen, or    sulfur;-   R³ is -T-R^(z), wherein:    -   T is a covalent bond or a bivalent C₁₋₁₂ saturated or        unsaturated, straight or branched, hydrocarbon chain, wherein        one or two methylene units of T are optionally and independently        replaced by —O—, —S—, —N(R)—, —C(O)—, —C(O)O—, —OC(O)—,        —N(R)C(O)—, —C(O)N(R)—, —S(O), —S(O)₂—, —N(R)SO₂—, or —SO₂N(R)—;        and    -   R^(z) is hydrogen, halogen, a monosaccharide, a disaccharide,        —OR, —SR, —NR₂, —N₃, or an optionally substituted group selected        from acyl, arylalkyl, heteroarylalkyl, C₁₋₆ aliphatic,        6-10-membered aryl, 5-10-membered heteroaryl having 1-4        heteroatoms independently selected from nitrogen, oxygen, or        sulfur, 4-7-membered heterocyclyl having 1-2 heteroatoms        independently selected from nitrogen, oxygen or sulfur; or        -   a hydrogen radical on R^(z) is replaced with a substituent            of the formula:

-   -   wherein each occurrence of R¹, R², R⁴, R⁵, R⁶, R⁷, T, and R^(z)        may be the same or different;

-   R⁴ is hydrogen, —OR, or ═O;

-   R⁵ and R⁶ are each independently selected from hydrogen, C₁₋₆    aliphatic, —SO₂R, —CO₂R; or R⁵ and R⁶ are taken together with their    intervening atoms to form an optionally substituted 5-7-membered    ring having 0-2 heteroatoms independently selected from nitrogen,    oxygen, or sulfur;

-   R⁷ is hydrogen, —OR, —OCO₂R, —OCOR, —OCOSR, or —OCONR₂; and

-   each R is independently hydrogen, an optionally substituted group    selected from acyl, arylalkyl, C₁₋₆ aliphatic, or C₁₋₆    heteroaliphatic having 1-2 heteroatoms independently selected from    nitrogen, oxygen, or sulfur, or:    -   two R on the same nitrogen atom are taken with the nitrogen to        form a 4-7-membered heterocyclic ring having 1-2 heteroatoms        independently selected from nitrogen, oxygen, or sulfur.

In certain embodiments, R¹ is optionally substituted C₁₋₆ aliphatic,—(CH₂)_(n)C(O)OR⁸, —(CH₂)_(n)C(O)N(R⁸)₂, —(CH₂)_(n)C(O)SR⁸, or takentogether with R² to form an optionally substituted, saturated orunsaturated 3-7-membered ring having 0-2 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur.

In some embodiments, R¹ is —(CH₂)_(n)C(O)OR⁸, wherein R⁸ is hydrogen, anoptionally substituted group selected from C₁₋₆ aliphatic or C₁₋₆heteroaliphatic having 1-2 hetero atoms independently selected fromnitrogen, oxygen, or sulfur; and n is an integer from 0-4, inclusive.

In some embodiments, R⁸ is an optionally substituted C₁₋₆ aliphaticgroup. In some embodiments, R⁸ is an optionally substituted C₁₋₃aliphatic group. In some embodiments, R⁸ is methyl. In some embodiments,R⁸ is ethyl. In some embodiments, R⁸ is CH₂F. In some embodiments, R⁸ isaryl. In some embodiments, R⁸ is

In some embodiments, R¹ is —(CH₂)_(n)C(O)N(R⁸)₂, and wherein each R⁸ isindependently hydrogen, an optionally substituted group selected fromC₁₋₆ aliphatic or C₁₋₆ heteroaliphatic having 1-2 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; and n is aninteger from 0-4, inclusive.

In some embodiments, R¹ is —(CH₂)_(n)C(O)N(R⁸)₂, and R⁸ is methyl.

In some embodiments, R¹ is —(CH₂)_(n)C(O)SR⁸, and wherein each R⁸ isindependently hydrogen, an optionally substituted group selected fromC₁₋₆ aliphatic or C₁₋₆ heteroaliphatic having 1-2 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; and n is aninteger from 0-4, inclusive.

In some embodiments, R¹ is —(CH₂)_(n)C(O)SR⁸, and R⁸ is ethyl.

In some embodiments, n is 0. In certain embodiments, n is 1 or 2. Insome embodiments, n is 1. In certain embodiments, n is 2. In someembodiments, n is 3. In some embodiments, n is 4.

In certain embodiments, R¹ is taken together with R² to form anoptionally substituted, saturated or unsaturated 3-7-membered ringhaving 0-2 heteroatoms independently selected from nitrogen, oxygen, orsulfur.

In some embodiments, R¹ and R² are taken together to form a saturated3-5-membered ring having 1-2 heteroatoms independently selected fromnitrogen or oxygen. In some embodiments, R¹ and R² are taken together toform a saturated 4-membered ring having 1 oxygen atom. In someembodiments, R¹ and R² are taken together to form:

In some embodiments, R¹ and R² are taken together to form:

In certain embodiments, R² is hydrogen, —SR, —NR₂, —OR, or an optionallysubstituted group selected from C₁₋₆ aliphatic, or C₁₋₆ heteroaliphatichaving 1-2 heteroatoms independently selected from nitrogen, oxygen, orsulfur.

In certain embodiments, R² is —NR₂ or —OR, wherein each R isindependently hydrogen, an optionally substituted group selected fromacyl, arylalkyl, C₁₋₆ aliphatic, or C₁₋₆ heteroaliphatic having 1-2heteroatoms independently selected from nitrogen, oxygen, or sulfur, ortwo R on the same nitrogen atom are taken together with the nitrogen toform a 4-7-membered heterocyclic ring having 1-2 heteroatomsindependently selected from nitrogen, oxygen, or sulfur.

In some embodiments, R² is —OR, wherein R is H. In some embodiments, R²is —OR, wherein R is acyl. In some embodiments, R² is —OR, wherein R isoptionally substituted C₁₋₆ aliphatic. In some embodiments, R² is —OR,wherein R is methyl.

In some embodiments, R² is —NR₂, wherein each R is independentlyhydrogen or optionally substituted C₁₋₆ aliphatic. In some embodiments,R² is —NR₂, wherein each R is hydrogen.

As generally described above, R³ is -T-R^(z), wherein:

-   -   T is a covalent bond or a bivalent C₁₋₁₂ saturated or        unsaturated, straight or branched, hydrocarbon chain, wherein        one or two methylene units of T are optionally and independently        replaced by —O—, —S—, —N(R)—, —C(O)—, —C(O)O—, —OC(O)—,        —N(R)C(O)—, —C(O)N(R)—, —S(O), —S(O)₂—, —N(R)SO₂—, or —SO₂N(R)—;        and    -   R^(z) is hydrogen, halogen, a monosaccharide, a disaccharide,        —OR, —SR, —NR₂, —N₃, or an optionally substituted group selected        from acyl, arylalkyl, heteroarylalkyl, C₁₋₆ aliphatic,        6-10-membered aryl, 5-10-membered heteroaryl having 1-4        heteroatoms independently selected from nitrogen, oxygen, or        sulfur; 4-7-membered heterocyclyl having 1-2 heteroatoms        independently selected from nitrogen, oxygen or sulfur; or        -   a hydrogen radical on R^(z) is replaced with a substituent            of the formula:

-   -   wherein each occurrence of R¹, R², R⁴, R⁵, R⁶, R⁷, T, and R^(z)        may be the same or different.

In certain embodiments, T is a bivalent C₁₋₁₂ saturated or unsaturated,straight or branched, hydrocarbon chain, wherein one methylene unit of Tis optionally and independently replaced by —O—, —S—, —N(R)—, —C(O)—,—C(O)O—, —OC(O)—, —N(R)C(O)—, —C(O)N(R)—, —S(O), —S(O)₂—, —N(R)SO₂—, or—SO₂N(R)—. In certain embodiments, T is a bivalent C₃₋₁₂ saturated orunsaturated, straight or branched, hydrocarbon chain. In someembodiments, T is selected from:

In certain embodiments, T is a bivalent C₁₋₁₂ saturated hydrocarbonchain, wherein one methylene unit of T is optionally and independentlyreplaced by —O—. In certain embodiments, T is a bivalent C₁₋₁₂unsaturated hydrocarbon chain, wherein one methylene unit of T isoptionally and independently replaced by —O—. In certain embodiments, Tis a bivalent C₁₋₁₀ saturated hydrocarbon chain, wherein one methyleneunit of T is optionally and independently replaced by —O—.

In some embodiments R^(z) is hydrogen, halogen, —OR, —SR, —NR₂, —N₃, amonosaccharide, a disaccharide, or an optionally substituted groupselected from acyl, arylalkyl, heteroarylalkyl, C₁₋₆ aliphatic,6-10-membered aryl, 5-10-membered heteroaryl having 1-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; 4-7-memberedheterocyclyl having 1-2 heteroatoms independently selected fromnitrogen, oxygen or sulfur; wherein each R is independently hydrogen oran optionally substituted group selected from acyl, arylalkyl, or C₁₋₆aliphatic.

In some embodiments, R^(z) is hydrogen or an optionally substitutedgroup selected from —OR, —NR₂, arylalkyl, heteroarylalkyl, C₁₋₆aliphatic, or 6-10-membered aryl. In some embodiments, R^(z) is —OR andR is benzyl. In some embodiments, R^(z) is —OR and R is methyl. In someembodiments, R^(z) is arylalkyl. In other embodiments, R^(z) isheteroarylalkyl. In some embodiments, R^(z) is —N₃. In otherembodiments, R^(z) is C₁₋₆ aliphatic. In other embodiments, R^(z) ishydrogen. In other embodiments, R^(z) is fluoro.

In some embodiments, a hydrogen radical on R^(z) is replaced with asubstituent corresponding to another unit of a compound of formula I,thereby forming a dimer. Exemplary dimer compounds are depicted in Table1, below.

In some embodiments, R^(z) is a saccharide group. In other embodiments,R^(z) is a disaccharide group. In some embodiments, R^(z) is

In some embodiments, R^(z) is

In certain embodiments, R⁴ is —OR, or ═O. In some embodiments, R⁴ is—OR, wherein R is hydrogen, acyl or C₁₋₆ aliphatic. In some embodiments,R⁴ is —OR, wherein R is C₁₋₆ aliphatic. In some embodiments, R⁴ is —OR,wherein R is methyl. In other embodiments, R⁴ is ═O. In someembodiments, R⁴ is OH.

In certain embodiments, R⁵ and R⁶ are each independently selected fromhydrogen, C₁₋₆ aliphatic, —S(O)₂R, or —C(O)OR. In some embodiments, R⁵and R⁶ are both hydrogen. In certain embodiments, at least one of R⁵ orR⁶ is hydrogen. In other embodiments, R⁵ and R⁶ are —C(O)OR, wherein Ris selected from hydrogen or C₁₋₆ aliphatic. In other embodiments, R⁵ is—S(O)₂R and R⁶ is hydrogen. In other embodiments, R⁶ is —S(O)₂R and R⁵is hydrogen. In some embodiments, R⁶ is —S(O)₂R, and R is phenyl.

In certain embodiments, R⁵ and R⁶ are taken together with theirintervening atoms to form an optionally substituted 5-7-membered ringhaving 0-2 heteroatoms independently selected from nitrogen, oxygen, orsulfur. In some embodiments, R⁵ and R⁶ are taken together with theirintervening atoms to form a C₅₋₆-membered ring having 1 heteroatomselected from nitrogen, oxygen, or sulfur. In some embodiments, R⁵ andR⁶ are both C₁₋₆ aliphatic and taken together with their interveningatoms to form an optionally substituted 5-7 membered ring.

In certain embodiments, R⁷ is hydrogen, —OR, —OC(O)OR, —OC(O)R,—OC(O)SR, or —OC(O)NR₂. In certain embodiments, R⁷ is hydrogen. In otherembodiments, R⁷ is —OC(O)OR, wherein R is selected from hydrogen or C₁₋₆aliphatic. In some embodiments, R⁷ is —OC(O)OR, wherein R is methyl.

In some embodiments, the invention provides compounds with increased ordecreased lipophilicity through the attachment of certain functionalgroups.

In some embodiments, the invention provides compounds with increasedcell permeability through the attachment of certain functional groups.Exemplary functional groups include, without limitation,

As described above for compounds of formula I, each

independently designates a single or double bond. In certainembodiments, such compounds of are formulae II-1, II-2, and II-3:

One of ordinary skill in the art will appreciate that compounds offormula I may possess a number of stereogenic centers. Unless otherwisestated, all stereoisomers of the compounds of the invention are withinthe scope of the invention. In certain embodiments, such compounds offormulae II-4, II-5, II-6 and II-7:

As described above and herein for compounds of formula I, R¹ may betaken together with R² to form an optionally substituted, saturated orunsaturated 3-7-membered ring having 0-2 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur. In certain embodiments, suchcompounds are of formula II-8:

One of ordinary skill in the art will appreciate that the tertiary aminepresent in compounds of formula I may be further derivitized into asalt, tertiary amine, or N-oxide. Such derivatives are comtemplated bythe invention and are within its scope. In some embodiments, suchcompounds are of formulae III-A and III-B:

or a pharmaceutically acceptable salt thereof, wherein:

-   each    independently designates a single or double bond;-   R¹ is hydrogen, optionally substituted C₁₋₆ aliphatic,    —(CH₂)_(n)CO₂R⁸, —(CH₂)_(n)CON(R⁸)₂, —(CH₂)_(n)COSR⁸, or taken    together with R² to form an optionally substituted, saturated or    unsaturated 3-7-membered ring having 0-2 heteroatoms independently    selected from nitrogen, oxygen, or sulfur; and    -   each R⁸ is independently hydrogen, an optionally substituted        group selected from cephalotaxine, C₁₋₆ aliphatic, 6-10-membered        aryl, or C₁₋₆ heteroaliphatic having 1-2 heteroatoms        independently selected from nitrogen, oxygen, or sulfur;    -   n is an integer from 0-4;-   R² is hydrogen, —NR₂, —OR, or an optionally substituted group    selected from acyl, C₁₋₆ aliphatic, or C₁₋₆ heteroaliphatic having    1-2 heteroatoms independently selected from nitrogen, oxygen, or    sulfur;-   R³ is -T-R^(z), wherein:    -   T is a covalent bond or a bivalent C₁₋₁₂ saturated or        unsaturated, straight or branched, hydrocarbon chain, wherein        one or two methylene units of T are optionally and independently        replaced by —O—, —S—, —N(R)—, —C(O)—, —C(O)O—, —OC(O)—,        —N(R)C(O)—, —C(O)N(R)—, —S(O), —S(O)₂—, —N(R)SO₂—, or —SO₂N(R)—;        and    -   R^(z) is hydrogen, halogen, a monosaccharide, a disaccharide,        —OR, —SR, —NR₂, —N₃, or an optionally substituted group selected        from acyl, arylalkyl, heteroarylalkyl, C₁₋₆ aliphatic,        6-10-membered aryl, 5-10-membered heteroaryl having 1-4        heteroatoms independently selected from nitrogen, oxygen, or        sulfur, 4-7-membered heterocyclyl having 1-2 heteroatoms        independently selected from nitrogen, oxygen or sulfur; or        -   a hydrogen radical on R^(z) is replaced with a substituent            of the formula:

-   -   -   wherein each occurrence of R¹, R², R⁴, R⁵, R⁶, R⁷, T, X, and            R^(z) may be the same or different;

-   R⁴ is hydrogen, —OR, or ═O;

-   R⁵ and R⁶ are each independently selected from hydrogen, C₁₋₆    aliphatic, —SO₂R, —CO₂R; or R⁵ and R⁶ are taken together with their    intervening atoms to form an optionally substituted 5-7-membered    ring having 0-2 heteroatoms independently selected from nitrogen,    oxygen, or sulfur;

-   R⁷ is hydrogen, —OR, —OCO₂R, —OCOR, —OCOSR, or —OCONR₂; and

-   each R is independently hydrogen, an optionally substituted group    selected from acyl, arylalkyl, C₁₋₆ aliphatic, or C₁₋₆    heteroaliphatic having 1-2 heteroatoms independently selected from    nitrogen, oxygen, or sulfur; or:    -   two R on the same nitrogen atom are taken with the nitrogen to        form a 4-7-membered heterocyclic ring having 1-2 heteroatoms        independently selected from nitrogen, oxygen, or sulfur;

-   R″ is hydrogen or an optionally substituted group selected from    acyl, arylalkyl, C₁₋₆ aliphatic, or C₁₋₆ heteroaliphatic having 1-2    heteroatoms independently selected from nitrogen, oxygen, or sulfur;    and

-   X is a suitable counter ion.

The ester side chain of natural cephalotaxus esters is appended off ofthe C3 carbon. One of ordinary skill will recognize that the ester sidechain may also be appended to other carbons on the cephalotaxine coreskeleton. In certain embodiments, such compounds are of formulae III-Cand III-D:

or a pharmaceutically acceptable salt thereof, wherein:

-   each    independently designates a single or double bond;-   R¹ is hydrogen, optionally substituted C₁₋₆ aliphatic,    —(CH₂)_(n)CO₂R⁸, —(CH₂)_(n)CON(R⁸)₂, —(CH₂)_(n)COSR⁸, or taken    together with R² to form an optionally substituted, saturated or    unsaturated 3-7-membered ring having 0-2 heteroatoms independently    selected from nitrogen, oxygen, or sulfur; and    -   each R⁸ is independently hydrogen, an optionally substituted        group selected from cephalotaxine, C₁₋₆ aliphatic, 6-10-membered        aryl, or C₁₋₆ heteroaliphatic having 1-2 heteroatoms        independently selected from nitrogen, oxygen, or sulfur;    -   n is an integer from 0-4;-   R² is hydrogen, —NR₂, —OR, or an optionally substituted group    selected from acyl, C₁₋₆ aliphatic, or C₁₋₆ heteroaliphatic having    1-2 heteroatoms independently selected from nitrogen, oxygen, or    sulfur;-   R³ is -T-R^(z), wherein:    -   T is a covalent bond or a bivalent C₁₋₁₂ saturated or        unsaturated, straight or branched, hydrocarbon chain, wherein        one or two methylene units of T are optionally and independently        replaced by —O—, —S—, —N(R)—, —C(O)—, —C(O)O—, —OC(O)—,        —N(R)C(O)—, —C(O)N(R)—, —S(O), —S(O)₂—, —N(R)SO₂—, or —SO₂N(R)—;        and    -   R^(z) is hydrogen, halogen, a monosaccharide, a disaccharide,        —OR, —SR, —NR₂, —N₃, or an optionally substituted group selected        from acyl, arylalkyl, heteroarylalkyl, C₁₋₆ aliphatic,        6-10-membered aryl, 5-10-membered heteroaryl having 1-4        heteroatoms independently selected from nitrogen, oxygen, or        sulfur, 4-7-membered heterocyclyl having 1-2 heteroatoms        independently selected from nitrogen, oxygen or sulfur; or        -   a hydrogen radical on R^(z) is replaced with a substituent            of the formula:

-   -   wherein each occurrence of R¹, R², R⁴, R⁵, R⁶, R⁷, T, X, and        R^(z) may be the same or different;

-   R⁴ is hydrogen, —OR, or ═O;

-   R⁵ and R⁶ are each independently selected from hydrogen, C₁₋₆    aliphatic, —SO₂R, —CO₂R; or R⁵ and R⁶ are taken together with their    intervening atoms to form an optionally substituted 5-7-membered    ring having 0-2 heteroatoms independently selected from nitrogen,    oxygen, or sulfur;

-   R⁷ is hydrogen, —OR, —OCO₂R, —OCOR, —OCOSR, or —OCONR₂; and

-   each R is independently hydrogen, an optionally substituted group    selected from acyl, arylalkyl, C₁₋₆ aliphatic, or C₁₋₆    heteroaliphatic having 1-2 heteroatoms independently selected from    nitrogen, oxygen, or sulfur; or:    -   two R on the same nitrogen atom are taken with the nitrogen to        form a 4-7-membered heterocyclic ring having 1-2 heteroatoms        independently selected from nitrogen, oxygen, or sulfur.

In certain embodiments, the synthesis of compound of formulae III-C andIII-D is carried out using suitable protecting groups as known in theart and as described by Greene, et al. (infra). Such protecting groupstrategies allow the placement of the ester side chain on differentcarbons of the cephalotaxine core at the discretion of one of ordinaryskill in the art.

In certain embodiments, compounds of formulae I, III-A, III-B, III-C, orIII-D have a c-log P value that may increase their multidrug resistanceratio. In certain embodiments, the c-log P value is at least about 0.95.In certain embodiments, the c-log P value is at least about 0.96. Incertain embodiments, the c-log P value is at least about 0.97. Incertain embodiments, the c-log P value is at least about 0.98. Incertain embodiments, the c-log P value is at least about 0.99. Incertain embodiments, the c-log P value is at least about 1.0. In certainembodiments, the c-log P value is at least about 1.1. In certainembodiments, the c-log P value is at least about 1.2. In certainembodiments, the c-log P value is at least about 1.3.

In certain embodiments, the c-log P value is about 0.95 to about 3.0. Incertain embodiments, the c-log P value is about 1.0 to about 3.0. Incertain embodiments, the c-log P value is about 1.2 to about 2.8. Incertain embodiments, the c-log P value is about 1.2 to about 2.4. Incertain embodiments, the c-log P value is about 1.9 to about 2.4. Incertain embodiments, the c-log P value is about 1.2 to about 1.3. Incertain embodiments, the c-log P value is about 1.9 to about 2.0. Incertain embodiments, the c-log P value is about 2.3 to about 2.4. Incertain embodiments, the c-log P value is about 2.75 to about 2.85.

Exemplary compounds of formula I are set forth in Table 1 below.

Table 1. Exemplary Compounds of Formula I

Synthesis of Compounds

Compounds of the invention may be synthesized according to the schemesdescribed below. The reagents and conditions described are intended tobe exemplary and not limiting. As one of skill in the art wouldappreciate, various analogs may be prepared by modifying the syntheticreactions such as using different starting materials, differentreagents, and different reaction conditions (e.g., temperature, solvent,concentration, etc.)

In one aspect, the present invention provides methods for the synthesisof intermediates as shown in Scheme 1, wherein each R^(x) isindependently halogen, —OR, or —NR₂; two R^(x) on adjacent carbon atomsmay be taken together to form a 5-7-membered ring;

-   each R is independently hydrogen, an optionally substituted group    selected from acyl, arylalkyl, C₁₋₆ aliphatic, or C₁₋₆    heteroaliphatic having 1-2 heteroatoms independently selected from    nitrogen, oxygen, or sulfur, or:    -   two R on the same nitrogen atom are taken with the nitrogen to        form a 4-7-membered heterocyclic ring having 1-2 heteroatoms        independently selected from nitrogen, oxygen, or sulfur;-   j is an integer from 0 to 4.

According to another aspect, the invention provides methods ofsynthesizing intermediates as shown in Scheme 2, wherein R^(x), R⁵, R⁶,and j are defined as described above and herein.

As described in Scheme 3, compounds of formula xvii may be synthesizedby reacting a compound of formula xiv with a suitable nucleophile, suchas a tetraalkylammonium halide, to give a compound of formula xv.Compound of formula xv may be transformed into compound of formula xviiby reaction with a halide such as fluorine, followed by cycloaddition ofa dipolarophile to azomethine ylide intermediate xvi.

Chloroeneones of formula xxiii may be prepared according to Scheme 4,wherein R⁴ and R⁷ are defined as described above and herein.

According to another aspect, compounds of formula xxv may be preparedaccording to Scheme 5.

In some embodiments, compounds of formula xxviii are prepared accordingto Scheme 6.

In some embodiments, compounds of formula xxx are prepared by reacting acompound of formula xxix under suitable desulfurization conditions toform a compound of formula xxx. Suitable desulfurization conditions areknown in the art and are described in March's Advanced Organic Chemistry(supra).

According to another aspect, compounds of formula xxxv may besynthesized as described in Scheme 8, wherein PG and PG¹ are suitableprotecting groups. While certain protecting groups are described inScheme 8, one of ordinary skill in the art will recognize that otherprotecting groups may be utilized.

Scheme 9 depicts the synthesis of compounds of formula xxxvi, whereinPG² represents a suitable protecting group. While certain protectinggroups are described, one of ordinary skill in the art will recognizethat other protecting groups may be utilized.

Scheme 10 depicts the synthesis of compounds of formulae xliii and xliv,wherein PG³ is a suitable protecting group and R⁸ is defined asdescribed above and herein. While certain protecting groups aredescribed, one of ordinary skill in the art will recognize that otherprotecting groups may be utilized.

Scheme 11 depicts the synthesis of compounds of formulae xlvii, xlviii,and xlix, wherein

-   T is a covalent bond or a bivalent C₁₋₁₂ saturated or unsaturated,    straight or branched, hydrocarbon chain, wherein one or two    methylene units of T are optionally and independently replaced by    —O—, —S—, —N(R)—, —C(O)—, —C(O)O—, —OC(O)—, —N(R)C(O)—, —C(O)N(R)—,    —S(O), —S(O)₂—, —N(R)SO₂—, or —SO₂N(R)—;-   PG³ is a suitable protecting group;-   R^(y) is hydrogen, halogen, a monosaccharide, a disaccharide, —OR,    —SR, —NR₂, —N₃, or an optionally substituted group selected from    acyl, arylalkyl, heteroarylalkyl, C₁₋₆ aliphatic, 6-10-membered    aryl, 5-10-membered heteroaryl having 1-4 heteroatoms independently    selected from nitrogen, oxygen, or sulfur, 4-7-membered heterocyclyl    having 1-2 heteroatoms independently selected from nitrogen, oxygen    or sulfur.

The PG, PG¹, PG², and PG³ groups on the formulae described above andherein are suitable protecting groups. Suitable amino and hydroxylprotecting groups are well known in the art and include those describedin detail in Protecting Groups in Organic Synthesis, T. W. Greene and P.G. M. Wuts, 3^(rd) edition, John Wiley & Sons, 1999, the entirety ofwhich is incorporated herein by reference. Suitable amino protectinggroups, taken with the —NH— moiety to which it is attached, include, butare not limited to, aralkylamines, carbamates, allyl amines, amides, andthe like. Examples of other protecting groups include t-butyloxycarbonyl(BOC), ethyloxycarbonyl, methyloxycarbonyl, trichloroethyloxycarbonyl,allyloxycarbonyl (Alloc), benzyloxocarbonyl (CBZ), allyl, benzyl (Bn),fluorenylmethylcarbonyl (Fmoc), acetyl, chloroacetyl, dichloroacetyl,trichloroacetyl, phenylacetyl, trifluoroacetyl, benzoyl, and the like.

Suitable protecting groups may be removed under conditions known in theart (see, for example, Greene, supra). One of ordinary skill in the artwill recognize that, under certain conditions, a protecting group may beremoved concomitantly with another chemical transformation. In someembodiments, the protecting group may be removed in a stepwise fashioneither before or after the other chemical transformation.

As described in Scheme 11, one aspect of the invention is to provide amethod of synthesizing compounds of formula I using a cross metathesisreaction. Thus, in certain embodiments, a method is provided comprisingthe steps of:

(a) providing a compound of formula A:

wherein:

-   R¹ is hydrogen, optionally substituted C₁₋₆ aliphatic,    —(CH₂)_(n)CO₂R⁸, —(CH₂)_(n)CON(R⁸)₂, —(CH₂)_(n)COSR⁸, or taken    together with R² to form an optionally substituted, saturated or    unsaturated 3-7-membered ring having 0-2 heteroatoms independently    selected from nitrogen, oxygen, or sulfur; and    -   each R⁸ is independently hydrogen, an optionally substituted        group selected from C₁₋₆ aliphatic or C₁₋₆ heteroaliphatic        having 1-2 heteroatoms independently selected from nitrogen,        oxygen, or sulfur;    -   n is an integer from 0-4;-   R² is hydrogen, —NR₂, —OR, or an optionally substituted group    selected from acyl, C₁₋₆ aliphatic, or C₁₋₆ heteroaliphatic having    1-2 heteroatoms independently selected from nitrogen, oxygen, or    sulfur;-   T is a covalent bond or a bivalent C₁₋₁₂ saturated or unsaturated,    straight or branched, hydrocarbon chain, wherein one or two    methylene units of T are optionally and independently replaced by    —O—, —S—, —N(R)—, —C(O)—, —C(O)O—, —OC(O)—, —N(R)C(O)—, —C(O)N(R)—,    —S(O), —S(O)₂—, —N(R)SO₂—, or —SO₂N(R)—;-   PG³ is a suitable protecting group; and-   each R is independently hydrogen, an optionally substituted group    selected from acyl, arylalkyl, C₁₋₆ aliphatic, or C₁₋₆    heteroaliphatic having 1-2 heteroatoms independently selected from    nitrogen, oxygen, or sulfur, or:    -   two R on the same nitrogen atom are taken with the nitrogen to        form a 4-7-membered heterocyclic ring having 1-2 heteroatoms        independently selected from nitrogen, oxygen, or sulfur; and        (b) treating said compound of formula A under suitable        conditions with a compound of formula B:

wherein:

-   R^(y) is hydrogen, halogen, a monosaccharide, a disaccharide, —OR,    —SR, —NR₂, —N₃, or an optionally substituted group selected from    acyl, arylalkyl, heteroarylalkyl, C₁₋₆ aliphatic, 6-10-membered    aryl, 5-10-membered heteroaryl having 1-4 heteroatoms independently    selected from nitrogen, oxygen, or sulfur, 4-7-membered heterocyclyl    having 1-2 heteroatoms independently selected from nitrogen, oxygen    or sulfur;    in the presence a suitable cross metathesis catalyst, to form a    compound of formula C:

In certain embodiments, step (b) provides a compound of formula A′:

One of ordinary skill in the art will recognize that a compound offormula A′ may be resubjected to cross metathesis conditions to provideadditional quantities of a compound of formula C. Thus, in certainembodiments, the present invention provides a method of treating saidcompound of formula A′ with a compound of formula B in the presence asuitable cross metathesis catalyst, to form a compound of formula C.

In another aspect, the present invention provides a method comprisingthe steps of

-   -   (a) providing a compound of formula C; and

-   -   (b) removing the PG³ moiety from a compound of formula C under        suitable conditions; and    -   (c) treating said compound of formula C under suitable        conditions with a compound of formula I-A:

wherein:

-   -   R⁵ and R⁶ are each independently selected from hydrogen, C₁₋₆        aliphatic, —SO₂R, —CO₂R, or R⁵ and R⁶ are taken together with        their intervening atoms to form an optionally substituted        5-7-membered ring having 0-2 heteroatoms independently selected        from nitrogen, oxygen, or sulfur;    -   R⁷ is hydrogen, —OR, —OCO₂R, —OCOR, —OCOSR, or —OCONR₂;    -   to form a compound of formula I-B:

In certain embodiments, the present invention provides a methodcomprising the steps of:

-   -   (a) providing a compound of formula A′; and

-   -   (b) removing the PG³ moiety from a compound of formula A′ under        suitable conditions; and    -   (c) treating said compound of formula A′ under suitable        conditions with a compound of formula I-A:

wherein:

-   -   R⁵ and R⁶ are each independently selected from hydrogen, C₁₋₆        aliphatic, —SO₂R, —CO₂R, or R⁵ and R⁶ are taken together with        their intervening atoms to form an optionally substituted        5-7-membered ring having 0-2 heteroatoms independently selected        from nitrogen, oxygen, or sulfur;    -   R⁷ is hydrogen, —OR, —OCO₂R, —OCOR, —OCOSR, or —OCONR₂;        to form a compound of formula I-B′:

In some embodiments, suitable conditions for the cross metathesisreaction may comprise the use of a suitable solvent. Suitable solventsinclude, but are not limited to, halogenated hydrocarbons and aromatichydrocarbons. In some embodiments, the solvent is dichloromethane. Insome embodiments, the solvent is benzene. In some embodiments, thesolvent is toluene.

In some embodiments, suitable conditions for the cross metathesisreaction are in the temperature range of about 10° C. to about 120° C.In some embodiments, the reaction proceeds at a temperature of about 25°C. to about 80° C. In some embodiments, the reaction proceeds at atemperature of about 10° C. to about 25° C. In some embodiments, thereaction proceeds at a temperature of about 25° C. to about 40° C. Insome embodiments, the reaction proceeds at reflux temperature reactionmixture.

One of ordinary skill in the art will recognize that compounds offormulae I-B and I-B′ may be subjected to suitable hydrogenationconditions (e.g., Pd/C, H₂; Wilkinson's catalyst; etc.) to providecompounds of formulae I-C and I-C′. Thus, in certain embodiments, thepresent invention provides a method of subjecting a compound of formulaeI-B or I-B′ to suitable hydrogenation conditions to provide a compoundof formulae I-C or I-C′:

As used herein, the term “suitable cross metathesis catalyst” refers toany catalyst known in the art to act as a catalyst for the crossmetathesis reaction of two olefin moieties. In certain embodiments, thecatalyst is a ruthenium alkylidene or ruthenium carbene. In someembodiments, the catalyst is a molybdenum-based species. In someembodiments, the catalyst is Grubbs 1^(st) generation. In someembodiments, the catalyst is Grubbs 2^(nd) generation. In someembodiments, the catalyst is Hoveyda-Grubbs 1^(st) generation. In someembodiments, the catalyst is Hoveyda-Grubbs 2^(nd) generation. In someembodiments, the catalyst isdichloro(3-methyl-2-butenylidene)bis(tricyclopentylphosphine)ruthenium(II). In some embodiments, the catalyst isdichloro(3-methyl-2-butenylidene)bis(tricyclohexylphosphine)ruthenium(II). In some embodiments, the catalyst is a chiral rutheniumcatalyst.

Methods of using and general descriptions of suitable cross metathesiscatalysts are described in Grubbs, R. H.; Tetrahedron, 2004, 7117-7140;Grubbs, R. H., et al.; Org. Lett., 2008, 441-444; the entire contents ofeach are hereby incorporated by reference.

Synthesis and Attachment of the Acyl Chain of Antitumor CephalotaxusEsters

The bulk of the synthetic reports concerning the cephalotaxus alkaloidshave focused on cephalotaxine. On the other hand, reports on thesynthesis of natural anti-leukemia cephalotaxus esters have beenrelatively scarce, likely a result of the difficulties associated withappending a fully intact acyl side chain onto the C3-OH ofcephalotaxine. The challenge of such an acylation arises from extensivesteric obstruction, marked by the secondary C3-hydroxyl nucleophileburied within the concave face of cephalotaxine, and exacerbated by afully α-substituted acyl electrophile in the side chain. Indeed, thedifficulty of this acylation event is highlighted in numeroussemi-syntheses of the cephalotaxus esters from cephalotaxine, whereinthe bulk of these efforts employed a less hindered prochiral C2′-sp²hybridized side chain derivative in the acylation event, followed bysubsequent non-stereoselective functional group manipulation. (K. L.Mikolajczak, C. R. Smith, Weislede. D, T. R. Kelly, J. C. McKenna andChristen. Pa, Tetrahedron Lett. 1974, 283-286; K. L. Mikolajczak and C.R. Smith, J. Org. Chem. 1978, 43, 4762-4765; S. Hiranuma and T.Hudlicky, Tetrahedron Lett. 1982, 23, 3431-3434; S. Hiranuma, M. Shibataand T. Hudlicky, J. Org. Chem. 1983, 48, 5321-5326) A notable exceptionto this strategy used an acyl chain substrate specifically appropriatefor homoharringtonine in which the C1″-ester moiety was constrained as acyclic derivative to allow for acylation with the C electrophile. (T. R.Kelly, R. W. McNutt, M. Montury, N. P. Tosches, K. L. Mikolajczak, C. R.Smith and D. Weisleder, J. Org. Chem. 1979, 44, 63-67) This approach wasintroduced with racemic substrates and has recently evolved tonon-racemic examples wherein enantio-enriched side chain substrates wereprepared in >10-step sequences. (J. P. Robin, R. Dhal, G. Dujardin, L.Girodier, L. Mevellec and S. Poutot, Tetrahedron Lett. 1999, 40,2931-2934)

Since the most pressing late-stage challenge in the synthesis of thecephalotaxus esters is the efficient attachment of hindered acyl chainderivatives, the present invention employs novel bond angle strainelements to these substrates to enable their use in high yieldingacylations of cephalotaxine. Without wishing to be bound by anyparticular theory, it is believed that constraining a fullyα-substituted acyl electrophile to a β-lactone relieves local stericcongestion at the electrophilic site; it may also engender greaterelectrophilicity through induction by imparting higher hybrid orbitals-character.

In certain embodiments, this strategy initially provides a synthesis ofdeoxyharringtonine. In some embodiments, the synthesis of other membersof this alkaloid class, namely anyhydroharringtonine, homoharringtonine,and homodeoxyharringtonine is provided. In other embodiments, thesynthesis of novel non-natural cephalotaxus esters is provided.

Anti-Proliferative Activity

The completion of the synthesis of deoxyharringtonine andanhydroharringtonine permitted, for the first time, an expandedevaluation of their in vitro cytotoxicity. Following the early screeningof the cephalotaxus esters against murine P388 and L1210 cell lines (R.G. Powell, Weislede. D and C. R. Smith, J. Pharm. Sci. 1972, 61, 1227),many of the cytotoxic evaluations focused on leukemia and lymphoma, withcomparatively fewer reports on activity profiles against solid tumorcell lines. (H. M. Kantarjian, M. Talpaz, V. Santini, A. Murgo, B.Cheson and S. M. O'Brien, Cancer 2001, 92, 1591-1605) As a result,deoxyharringtonine, anhydroharringtonine, and various non-naturalcephalotaxus ester derivatives were evaluated against a variety of humanhematopoietic and solid tumor cell lines (Table 2). (C. Antczak, D.Shum, S. Escobar, B. Bassit, E. Kim, V. E. Seshan, N. Wu, G. L. Yang, O.Ouerfelli, Y. M. Li, D. A. Scheinberg and H. Djaballah, J. Biomol.Screening 2007, 12, 521-535; D. Shum, C. Radu, E. Kim, M. Cajuste, Y.Shao, V. E. Seshan and H. Djaballah, Journal of Enzyme Inhibition andMedicinal Chemistry (in press)) These include HL-60 (acute promyelocyticleukemia), HL-60/RV+(a P-glycoprotein over-expressing multidrugresistant HL-60 variant which was selected by continuous exposure to thevinca alkaloid vincristine), JURKAT (T cell leukemia), ALL3 (acutelymphoblastic leukemia recently isolated from a patient treated at MSKCCand characterized as Philadelphia chromosome positive), NCEB1 (Mantlecell lymphoma), JEKO (B cell lymphoma), MOLT-3 (acute lymphoblasticT-cell), SKNLP (neuroblastoma), Y79 (retinoblastoma), PC9(adenocarcinoma), H1650 (adenocarcinoma), H1975 (adenocarcinoma), H2030(adenocarcinoma), H3255 (adenocarcinoma), TC71 (Ewing's sarcoma), HTB-15(glioblastoma), A431 (epithelial carcinoma), HeLa (cervicaladenocarcinoma), and WD0082 (well-differentiated liposarcoma).

Several general features are evident in the cytoxicity data accumulatedin the screening campaigns (Table 2). As expected, evaluation ofdeoxyharringtonine revealed exceedingly potent cytotoxic activityagainst all of the hematopoietic cell lines tested (HL-60, HL-60/RV+,JURKAT, ALL3, NCEB1, JEKO, MOLT-3); moreover, the alkaloid exhibitedsimilarly high activity against most of the solid tumor cell linestested (SKNLP, PC9, H1650, H1975, H2030, H3255, A431, HeLa, TC71,HTB-15, WD0082). Interestingly, the late-stage β-lactone variant I-3a(see also Scheme 13-1) exhibited significant cytotoxicity, yet atattenuated levels compared to the parent alkaloid 2, revealing theimportance of a hydroxyl group or an H-bond donor functionality at theC2′-position. Surprisingly, the cytoxicity profile ofanhydroharringtonine revealed fairly poor antitumor activity. While anearly report noted comparable cytotoxic activity of anhydroharringtonineto that of deoxyharringtonine against murine P388, (Wang, 1992, supra)the present result indicates that the activity of anhydroharringtonineis generally several orders of magnitude lower in human HL-60 tumorcells. This unimpressive potency level of anhydroharringtonine isconsistent with the desire for a 2′-hydroxy group or other suitableH-bond donor in the acyl chain to confer adequate activity (vide supra).

TABLE 2 Cytotoxicity of deoxyharringtonine, β-lactone I-3a andanhydroharringtonine. Cmpd I-3a Cell Line 2 IC₅₀ (μM) IC₅₀ (μM) 5 IC₅₀(μM) HL-60 0.02 2.68 22.7 HL-60/RV+ 0.22 21.8 >100 JURKAT 0.04 5.7142.99 ALL3 <0.1** 1.47 >100 NCEB1 0.07 8.62 >100 JEKO 0.08 10.48 >100MOLT-3 0.02 2.68 26.83 SKNLP <0.1** 6.46 5.34 Y79 70.59 >100 >100 PC90.03 4.23 29.08 H1650 0.04 4.53 N.A. H1975 0.06 8.42 N.A. H2030 0.107.72 N.A. H3255 0.08 5.55 N.A. A431 0.06 N.A. N.A. HeLa 0.04 N.A. N.A.TC71 0.06 12 >100 HTB-15 0.20 52 >100 WD0082 0.10 5 >100 *Highestcompound concentration tested. **Lowest compound concentration testedand yielding 100% cellular killing.Multidrug Resistant Cancer

The development of vincristine-resistance in cancer cells, such asHL-60/RV+ (Table 2), is believed to arise from classic multidrugresistance (MDR). This involves the overexpression of ATP-dependentefflux pumps, such as P-glycoprotein (Pgp) and multidrugresistance-associated protein (MRP), leading to expulsion of naturalproduct hydrophobic drugs (e.g., vinca alkaloids, anthracyclines,actinomycin-D, paclitaxel) from the cell. (M. M. Gottesman, T. Fojo andS. E. Bates, Nat. Rev. Cancer 2002, 2, 48-58) Previous reports havenoted that the activity of homoharringtonine (HHT), the cephalotaxusester currently being evaluated in clinical trials, is also compromisedin MDR human leukemia cells. (Benderra, supra) The susceptibility of MDRcancer cells to different cephalotaxus esters has not beensystematically probed previously. Prevention of MDR would significantlyimprove therapeutic response to this family of chemotherapeutics andextend their use in the clinic. One possible way to achieve this wouldbe to develop anticancer agents that are not substrates for theseATP-dependent transporters, thus overcoming their efflux from cells.

In examining variations in potencies of deoxyharringtonine against thisextensive panel of cell lines (Table 2), it is worth noting that itsactivity against vincristine-resistant HL-60/RV+ cells (IC₅₀ 0.22 μM),relative to its non-resistant counterpart HL-60 (IC₅₀ 0.02 μM), showsonly a ˜10-fold decrease in potency. This trend is also reflected in theβ-lactone derivative I-3a (albeit with lower absolute cytotoxicitylevels). This rather low observed 10-fold resistance index spawned aninterest in probing potential molecular design criteria that may offsetMDR susceptibility in this class of alkaloids. The current syntheticapproach to deoxyharringtonine permits the rapid and versatileattachment of sterically demanding acyl chains onto the cephalotaxinecore. Thus, the synthetic strategy to deoxyharringtonine was furtherextended to the construction of two additional anti-leukemiacephalotaxus ester natural products, namely homoharringtonine andhomodeoxyharringtonine, all reported to be potent anti-leukemiaalkaloids.

As described above and herein, certain aspects of the present inventionprovide the syntheses of the natural cephalotaxus esters 2-4 (seeFIG. 1) together with two non-natural synthetic analogues, such asbenzyldehydrohomoharringtonine I-5 and bis(demethyl)deoxyharringtonineI-4, and further permits their comparative biological evaluation against“sensitive” and MDR tumor cell lines (see FIGS. 3 and 4). When testedagainst the “sensitive” HL-60 cell line, all were found to beexceedingly potent (IC₅₀<0.08 μM). When evaluated against the“resistant” HL60/RV+ cell line, stark differential response levels wereobserved within this collection of cephalotaxus esters (FIG. 4).Interestingly homoharringtonine (3) displayed a 125-fold decrease inactivity toward HL-60/RV+ relative to that of HL-60 (resistanceindex=125). By contrast, much lower resistance indices of 11, 3, 12, and19 were observed with the esters 2, 4, I-5, and I-4, respectively,indicating that these latter natural and non-natural products aresignificantly less susceptible to MDR. While not wishing to be bound byany particular theory, one possible explanation for the high MDRsusceptibility of homoharringtonine (3) is its decreased lipophilicityas a consequence of its acyl chain structure, thereby rendering it agood substrate for the efflux pumps.

The relationship of the calculated lipophilicity values (c-log P) to theresistance indices for the highly potent cephalotaxus esters 2-4, I-5,and I-4 is presented in FIG. 4, wherein compounds with c-log P valuesgreater than 1.2 lead to generally low susceptibility to MDR (i.e.,resistance indices ≦19 for the cephalotaxus esters 2, 4, I-5, and I-4).The exception is homoharringtonine (3), exhibiting a relatively lowc-log P value (0.95, relatively more polar) to reflect an increasedsusceptibility to MDR (i.e., resistance index 125). Thus, in certainaspects, the present invention provides for the first time new insightsinto the contribution of acyl chain structure modification towardovercoming MDR resistance for this class of compounds.

It is worth emphasizing that the only structural difference on the acylchain between homoharringtonine (3) and homodeoxyharringtonine (4) is ahydroxyl group at the 6′-position (FIG. 4). While only a minorstructural perturbation, this 6′-substitution difference drasticallyaffects the lipophilicity of the molecules, ranging from a c-log P valueof 0.95 (polar) for 3 to a more hydrophobic compound 4 with a c-log Pvalue of 2.33 (i.e., FIG. 5). Importantly, with a resistance index ofonly 3 (as in the case with homodeoxyharringtonine 4), both comparativecell lines can be “sensitive” to the compound of interest. As aconsequence, this minor structural variation from 3 to 4 has allowed foreffective quelling of MDR resistance in this cell line. Given thisfinding, it is thus surprising that despite its MDR liability,homoharringtonine (3) is employed as the favored cephalotaxus ester foradvancement in the clinic, exemplified by a current phase III clinicprospective trial with 3 for use as a combination therapy for chronicmyeloid leukemia. (L. Legros, S. Hayette, F. E. Nicolini, S. Raynaud, K.Chabane, J. P. Magaud, J. P. Cassuto and M. Michallet, Leukemia 2007,21, 2204-2206) One practical reason for this may lie in the increasednatural abundance of homoharringtonine (3) relative to othercephalotaxus esters. (R. G. Powell, Phytochemistry 1972, 11, 1467)Moreover, semisynthetic sources of homoharringtonine have built on theseminal work of Kelly, wherein the 6′-oxygen functionality is aprerequisite for efficient acyl chain attachment to cephalotaxine.(Kelly, 1989, supra) Notably, this semi-synthetic approach is uniquelysuited for homoharringtonine (3). Fortunately, the synthetic strategiesdescribed herein enable unfettered access to other, more therapeuticallyviable cephalotaxus esters, for the development of additional compoundsfor the treatment of leukemia and other proliferative diseases.

Resistance of Vincristine-Sensitive Y79 Retinoblastoma to CephalotaxusEsters

In the initial cytotoxicity evaluation (Table 1), it is also worthhighlighting that the Y79 retinoblastoma cell line uniquely showedsignificant resistance to both deoxyharringtonine (2) and its β-lactonederivative I-3a. Indeed, this selective resistance of Y79 may be ageneral phenomenon (Table 3) as evaluation with a few other activecytotoxic non-natural synthetic cephalotaxus ester analogues, includingthe benzyldehydrohomoharringtonine I-5, the β-lactone ester I-1, andbis(demethyl)deoxyharringtonine I-4. All of these compounds behavedsimilarly to that of deoxyharringtonine (2) and its β-lactone derivativeI-3a (cf. Table 2), exhibiting broad spectrum cytoxicity with theexception of the Y79 cell line, to which the molecules were essentiallyimpotent.

TABLE 3 Cmpd I-1 Cell Line I-5 IC₅₀ (μM) IC₅₀ (μM) I-4 IC₅₀ (μM) HL-600.01 5.73 0.08 HL-60/RV+ 0.19 40.30 0.80 JURKAT 0.03 12.01 0.19 ALL3<0.01 4.24 0.16 NCEB1 0.06 39.24 0.50 JEKO 0.08 25.1 0.56 MOLT3 0.016.41 0.06 SKNLP <0.01 10.04 0.11 Y79 >100 >100 >100 PC9 0.04 11.29 0.13TC71 0.03 24 0.20 HTB-15 0.10 58 0.50 WD0082 0.05 11 0.20

Though this specific lack of cytotoxicity in Y79 could also beattributed to the overexpression of multidrug resistance genes (MDR),Conway and co-workers have reported the Y79 cell line to be sensitive tovincristine with an IC₅₀ value of approx 0.8 μM. (R. M. Conway, M. C.Madigan, F. A. Billson and P. L. Penfold, Eur. J. Cancer 1998, 34,1741-1748) Furthermore, a comparative microarray analysis of the Y79cell line with normal retinal tissue detected up-regulation of severalgenes typically found to be markers of stem cell-like characteristicsincluding the mdr gene ABCG2. (G. M. Seigel, A. S. Hackam, A. Ganguly,L. M. Mandell and F. Gonzalez-Fernandez, Mol. Vis. 2007, 13, 823-832)Without wishing to be bound by any particular theory, we postulate thatperhaps the mechanism of resistance to cephalotaxus esters by Y79 is notentirely mediated through the classical ATP-dependent efflux pumps alonebut rather through an as yet unknown mechanism involving stem cell-likecharacteristics. This is consistent with the hypothesis that theappearance of subsequent tumors in leukemias, brain tumors, breastcancer, lung cancer, as well as many other cancers, is linked to thepersistence of cancer stem cells. This observation suggests thatdesigned cephalotaxus esters have the potential to serve as smallmolecule probes for interrogating the genetic basis of this highlyresilient retinoblastoma cell line as well as potentially shedding somelight on how to overcome this persistence phenomena in these dormantprogenitor cancer stem cells.

The development, optimization, and application of novel syntheticstrategies have enabled the synthesis of the potent anti-leukemia agents(−)-deoxyharringtonine (2), (−)-homoharringtonine (3),(−)-homodeoxyharringtonine (4), and (−)-anhydroharringtonine (5).Several advances served as key elements in the preparation of(−)-cephalotaxine (1) and should find general applicability in complexN-heterocycle synthesis. Efforts to advance these synthetic pursuitsbeyond that of (−)-1 to that of the rare anti-neoplastic C3-O-esterderivatives have led to an efficient non-racemic synthesis of novelcephalotaxus acyl chains. Construction of strained β-lactoneintermediates enabled late-stage C3-O-acylation of cephalotaxine, along-standing challenge in the synthesis of sterically congestedbioactive cephalotaxus esters. This technology enabled cytotoxicityscreening of natural and non-natural cephalotaxus esters against anexpansive array of human hematopoietic and solid tumor cell lines. Theseevaluations were instrumental in discovering novel non-naturalcephalotaxus esters with potent antitumor effects. Moreover, theseefforts have uncovered the potential of specific members of this familyof alkaloids to overcome resistance in MDR HL-60/RV+ tumor cells throughthe preparation of acyl chain variants, uniquely made available with bythe invention's acyl chain attachment approach. Thus, in one aspect, thepresent invention provides new avenues for molecular design of thesealkaloids to offset multi-drug resistance, offering new lines ofchemotherapeutic defense against leukemia and other cancers.

Radiolabeling

It has been found that ¹⁸F-fluoroiodomethane (¹⁸FCH₂I) is a usefulintermediate for the fluorination of organic intermediates. See Zheng etal., J. Nucl. Med., 38: 177P (Abs. 761) (1997), the entire contents ofwhich are hereby incorporated by reference. The resulting ¹⁸F-labeledmolecules are useful in imaging targeted tissue by clinical positronemission tomography. In certain embodiments, compounds of formulae I,III-A, III-B, III-C, or III-D may be derivatized for radiolabeling viathe incorporation of one or more —CH₂ ¹⁸F groups, or derivativesthereof.

Click Chemistry

“Click chemistry” is well known in the art and is useful in some aspectsof the present invention. Click chemistry embodies versatilecycloaddition reactions between azides and alkynes that enable a numberof useful applications. Methods of carrying out click chemistry areknown in the art, and are described by Kolb, H. C.; Sharpless, K. B.,Drug Disc. Today, 2003, 1128-1137; Moses, J. E.; Moorhouse, A. D.; Chem.Soc. Rev., 2007, 1249-1262; the entire contents of each are herebyincorporated by reference. In some embodiments, compounds of formulae I,III-A, III-B, III-C, or III-D contain a azide moiety that may be reactedwith an alkyne under conditions suitable for click chemistry. In someembodiments, compounds of formulae I, III-A, III-B, III-C, or III-Dcontain an alkyne moiety that may be reacted with an azide underconditions suitable for click chemistry. In certain embodiments, theclick chemistry reaction appends a functional group to a compound offormulae I, III-A, III-B, III-C, or III-D. In certain embodiments, theclick chemistry reaction appends a targeting moiety to a compound offormulae I, III-A, III-B, III-C, or III-D. In certain embodiments, theclick chemistry reaction appends a labeling moiety to a compound offormulae I, III-A, III-B, III-C, or III-D.

Definitions

As used herein, the following definitions shall apply unless otherwiseindicated.

The term “aliphatic” or “aliphatic group,” as used herein, means astraight-chain (i.e., unbranched) or branched, substituted orunsubstituted hydrocarbon chain that is completely saturated or thatcontains one or more units of unsaturation, or a monocyclic hydrocarbonor bicyclic hydrocarbon that is completely saturated or that containsone or more units of unsaturation, but which is not aromatic (alsoreferred to herein as “carbocycle,” “cycloaliphatic” or “cycloalkyl”),that has a single point of attachment to the rest of the molecule.Unless otherwise specified, aliphatic groups contain 1-6 aliphaticcarbon atoms. In some embodiments, aliphatic groups contain 1-5aliphatic carbon atoms. In other embodiments, aliphatic groups contain1-4 aliphatic carbon atoms. In still other embodiments, aliphatic groupscontain 1-3 aliphatic carbon atoms, and in yet other embodiments,aliphatic groups contain 1-2 aliphatic carbon atoms. In someembodiments, “cycloaliphatic” (or “carbocycle” or “cycloalkyl”) refersto a monocyclic C₃-C₆ hydrocarbon that is completely saturated or thatcontains one or more units of unsaturation, but which is not aromatic,that has a single point of attachment to the rest of the molecule.Suitable aliphatic groups include, but are not limited to, linear orbranched, substituted or unsubstituted alkyl, alkenyl, alkynyl groupsand hybrids thereof such as (cycloalkyl)alkyl, (cycloalkenyl)alkyl or(cycloalkyl)alkenyl.

The term “lower alkyl” refers to a C₁₋₄ straight or branched alkylgroup. Exemplary lower alkyl groups are methyl, ethyl, propyl,isopropyl, butyl, isobutyl, and tert-butyl.

The term “lower haloalkyl” refers to a C₁₋₄ straight or branched alkylgroup that is substituted with one or more halogen atoms.

The term “heteroatom” means one or more of oxygen, sulfur, nitrogen,phosphorus, or silicon (including, any oxidized form of nitrogen,sulfur, phosphorus, or silicon; the quaternized form of any basicnitrogen or; a substitutable nitrogen of a heterocyclic ring, forexample N (as in 3,4-dihydro-2H-pyrrolyl), NH (as in pyrrolidinyl) orNR⁺ (as in N-substituted pyrrolidinyl)).

The term “unsaturated,” as used herein, means that a moiety has one ormore units of unsaturation.

As used herein, the term “bivalent C₁₋₁₂ (or C₁₋₁₀, C₃₋₁₂) or saturatedor unsaturated, straight or branched, hydrocarbon chain,” refers tobivalent alkylene, alkenylene, and alkynylene chains that are straightor branched as defined herein.

The term “alkylene” refers to a bivalent alkyl group. An “alkylenechain” is a polymethylene group, i.e., —(CH₂)_(n)—, wherein n is apositive integer, preferably from 1 to 6, from 1 to 4, from 1 to 3, from1 to 2, or from 2 to 3. A substituted alkylene chain is a polymethylenegroup in which one or more methylene hydrogen atoms are replaced with asubstituent. Suitable substituents include those described below for asubstituted aliphatic group.

The term “alkenylene” refers to a bivalent alkenyl group. A substitutedalkenylene chain is a polymethylene group containing at least one doublebond in which one or more hydrogen atoms are replaced with asubstituent. Suitable substituents include those described below for asubstituted aliphatic group.

The term “alkynylene” refers to a bivalent alkynyl group. A substitutedalkynylene chain is a polymethylene group containing at least one doublebond in which one or more hydrogen atoms are replaced with asubstituent. Suitable substituents include those described below for asubstituted aliphatic group.

The term “acyl,” used alone or a part of a larger moiety, refers togroups formed by removing a hydroxy group from a carboxylic acid.Exemplary acyl groups include, without limitation, —C(═O)Me, —C(═O)Et,—C(═O)i-Pr, —C(═O)aryl, and —C(═O)CH₂F.

The term “halogen” means F, Cl, Br, or I.

The terms “aralkyl” and “arylalkyl” are used interchangably and refer toalkyl groups in which a hydrogen atom has been replaced with an arylgroup. Such groups include, without limitation, benzyl, cinnamyl, anddihyrocinnamyl.

The term “aryl” used alone or as part of a larger moiety as in“aralkyl,” “aralkoxy,” or “aryloxyalkyl,” refers to monocyclic orbicyclic ring systems having a total of five to fourteen ring members,wherein at least one ring in the system is aromatic and wherein eachring in the system contains 3 to 7 ring members. The term “aryl” may beused interchangeably with the term “aryl ring.”

In certain embodiments of the present invention, “aryl” refers to anaromatic ring system which includes, but not limited to, phenyl,biphenyl, naphthyl, anthracyl and the like, which may bear one or moresubstituents. Also included within the scope of the term “aryl,” as itis used herein, is a group in which an aromatic ring is fused to one ormore non-aromatic rings, such as indanyl, phthalimidyl, naphthimidyl,phenanthridinyl, or tetrahydronaphthyl, and the like.

The terms “heteroaryl” and “heteroar-,” used alone or as part of alarger moiety, e.g., “heteroaralkyl,” or “heteroaralkoxy,” refer togroups having 5 to 10 ring atoms, preferably 5, 6, or 9 ring atoms;having 6, 10, or 14 π electrons shared in a cyclic array; and having, inaddition to carbon atoms, from one to five heteroatoms. The term“heteroatom” refers to nitrogen, oxygen, or sulfur, and includes anyoxidized form of nitrogen or sulfur, and any quaternized form of a basicnitrogen. Heteroaryl groups include, without limitation, thienyl,furanyl, pyrrolyl, imidazolyl, pyrazolyl, triazolyl, tetrazolyl,oxazolyl, isoxazolyl, oxadiazolyl, thiazolyl, isothiazolyl,thiadiazolyl, pyridyl, pyridazinyl, pyrimidinyl, pyrazinyl, indolizinyl,purinyl, naphthyridinyl, and pteridinyl. The terms “heteroaryl” and“heteroar-”, as used herein, also include groups in which aheteroaromatic ring is fused to one or more aryl, cycloaliphatic, orheterocyclyl rings, where the radical or point of attachment is on theheteroaromatic ring. Nonlimiting examples include indolyl, isoindolyl,benzothienyl, benzofuranyl, dibenzofuranyl, indazolyl, benzimidazolyl,benzthiazolyl, quinolyl, isoquinolyl, cinnolinyl, phthalazinyl,quinazolinyl, quinoxalinyl, 4H-quinolizinyl, carbazolyl, acridinyl,phenazinyl, phenothiazinyl, phenoxazinyl, tetrahydroquinolinyl,tetrahydroisoquinolinyl, and pyrido[2,3-b]-1,4-oxazin-3(4H)-one. Aheteroaryl group may be mono- or bicyclic. The term “heteroaryl” may beused interchangeably with the terms “heteroaryl ring,” “heteroarylgroup,” or “heteroaromatic,” any of which terms include rings that areoptionally substituted. The terms “heteroaralkyl” and “heteroarylalkyl”refer to an alkyl group substituted by a heteroaryl moiety, wherein thealkyl and heteroaryl portions independently are optionally substituted.

The term “heteroaliphatic,” as used herein, means aliphatic groupswherein one or two carbon atoms are independently replaced by one ormore of oxygen, sulfur, nitrogen, or phosphorus. Heteroaliphatic groupsmay be substituted or unsubstituted, branched or unbranched, cyclic oracyclic, and include “heterocycle,” “heterocyclyl,”“heterocycloaliphatic,” or “heterocyclic” groups.

As used herein, the terms “heterocycle,” “heterocyclyl,” “heterocyclicradical,” and “heterocyclic ring” are used interchangeably and refer toa stable 5- to 7-membered monocyclic or 7-10-membered bicyclicheterocyclic moiety that is either saturated or partially unsaturated,and having, in addition to carbon atoms, one or more, preferably one tofour, heteroatoms, as defined above. When used in reference to a ringatom of a heterocycle, the term “nitrogen” includes a substitutednitrogen. As an example, in a saturated or partially unsaturated ringhaving 0-3 heteroatoms selected from oxygen, sulfur or nitrogen, thenitrogen may be N (as in 3,4-dihydro-2H-pyrrolyl), NH (as inpyrrolidinyl), or ⁺NR (as in N-substituted pyrrolidinyl).

A heterocyclic ring can be attached to its pendant group at anyheteroatom or carbon atom that results in a stable structure and any ofthe ring atoms can be optionally substituted. Examples of such saturatedor partially unsaturated heterocyclic radicals include, withoutlimitation, tetrahydrofuranyl, tetrahydrothiophenyl pyrrolidinyl,piperidinyl, pyrrolinyl, tetrahydroquinolinyl, tetrahydroisoquinolinyl,decahydroquinolinyl, oxazolidinyl, piperazinyl, dioxanyl, dioxolanyl,diazepinyl, oxazepinyl, thiazepinyl, morpholinyl, and quinuclidinyl. Theterms “heterocycle,” “heterocyclyl,” “heterocyclyl ring,” “heterocyclicgroup,” “heterocyclic moiety,” and “heterocyclic radical,” are usedinterchangeably herein, and also include groups in which a heterocyclylring is fused to one or more aryl, heteroaryl, or cycloaliphatic rings,such as indolinyl, 3H-indolyl, chromanyl, phenanthridin yl, ortetrahydroquinolinyl, where the radical or point of attachment is on theheterocyclyl ring. A heterocyclyl group may be mono- or bicyclic. Theterm “heterocyclylalkyl” refers to an alkyl group substituted by aheterocyclyl, wherein the alkyl and heterocyclyl portions independentlyare optionally substituted.

As used herein, the term “partially unsaturated” refers to a ring moietythat includes at least one double or triple bond. The term “partiallyunsaturated” is intended to encompass rings having multiple sites ofunsaturation, but is not intended to include aryl or heteroarylmoieties, as herein defined.

In another aspect, the present invention provides “pharmaceuticallyacceptable” compositions, which comprise a therapeutically effectiveamount of one or more of the compounds described herein, formulatedtogether with one or more pharmaceutically acceptable carriers(additives) and/or diluents. As described in detail, the pharmaceuticalcompositions of the present invention may be specially formulated foradministration in solid or liquid form, including those adapted for thefollowing: oral administration, for example, drenches (aqueous ornon-aqueous solutions or suspensions), tablets, e.g., those targeted forbuccal, sublingual, and systemic absorption, boluses, powders, granules,pastes for application to the tongue; parenteral administration, forexample, by subcutaneous, intramuscular, intravenous or epiduralinjection as, for example, a sterile solution or suspension, orsustained-release formulation; topical application, for example, as acream, ointment, or a controlled-release patch or spray applied to theskin, lungs, or oral cavity; intravaginally or intrarectally, forexample, as a pessary, cream or foam; sublingually; ocularly;transdermally; or nasally, pulmonary and to other mucosal surfaces.

The phrase “pharmaceutically acceptable” is employed herein to refer tothose compounds, materials, compositions, and/or dosage forms which are,within the scope of sound medical judgment, suitable for use in contactwith the tissues of human beings and animals without excessive toxicity,irritation, allergic response, or other problem or complication,commensurate with a reasonable benefit/risk ratio.

The phrase “pharmaceutically-acceptable carrier” as used herein means apharmaceutically-acceptable material, composition or vehicle, such as aliquid or solid filler, diluent, excipient, or solvent encapsulatingmaterial, involved in carrying or transporting the subject compound fromone organ, or portion of the body, to another organ, or portion of thebody. Each carrier must be “acceptable” in the sense of being compatiblewith the other ingredients of the formulation and not injurious to thepatient. Some examples of materials which can serve aspharmaceutically-acceptable carriers include: sugars, such as lactose,glucose and sucrose; starches, such as corn starch and potato starch;cellulose, and its derivatives, such as sodium carboxymethyl cellulose,ethyl cellulose and cellulose acetate; powdered tragacanth; malt;gelatin; talc; excipients, such as cocoa butter and suppository waxes;oils, such as peanut oil, cottonseed oil, safflower oil, sesame oil,olive oil, corn oil and soybean oil; glycols, such as propylene glycol;polyols, such as glycerin, sorbitol, mannitol and polyethylene glycol;esters, such as ethyl oleate and ethyl laurate; agar; buffering agents,such as magnesium hydroxide and aluminum hydroxide; alginic acid;pyrogen-free water; isotonic saline; Ringer's solution; ethyl alcohol;pH buffered solutions; polyesters, polycarbonates and/or polyanhydrides;and other non-toxic compatible substances employed in pharmaceuticalformulations.

As used herein, the term “pharmaceutically acceptable salt” refers tothose salts which are, within the scope of sound medical judgment,suitable for use in contact with the tissues of humans and lower animalswithout undue toxicity, irritation, allergic response and the like, andare commensurate with a reasonable benefit/risk ratio. Pharmaceuticallyacceptable salts are well known in the art. For example, S. M. Berge etal., describe pharmaceutically acceptable salts in detail in J.Pharmaceutical Sciences, 1977, 66, 1-19, incorporated herein byreference. Pharmaceutically acceptable salts of the compounds of thisinvention include those derived from suitable inorganic and organicacids and bases. Examples of pharmaceutically acceptable, nontoxic acidaddition salts are salts of an amino group formed with inorganic acidssuch as hydrochloric acid, hydrobromic acid, phosphoric acid, sulfuricacid and perchloric acid or with organic acids such as acetic acid,oxalic acid, maleic acid, tartaric acid, citric acid, succinic acid ormalonic acid or by using other methods used in the art such as ionexchange. Other pharmaceutically acceptable salts include adipate,alginate, ascorbate, aspartate, benzenesulfonate, benzoate, bisulfate,borate, butyrate, camphorate, camphorsulfonate, citrate,cyclopentanepropionate, digluconate, dodecylsulfate, ethanesulfonate,formate, fumarate, glucoheptonate, glycerophosphate, gluconate,hemisulfate, heptanoate, hexanoate, hydroiodide,2-hydroxy-ethanesulfonate, lactobionate, lactate, laurate, laurylsulfate, malate, maleate, malonate, methanesulfonate,2-naphthalenesulfonate, nicotinate, nitrate, oleate, oxalate, palmitate,pamoate, pectinate, persulfate, 3-phenylpropionate, phosphate, pivalate,propionate, stearate, succinate, sulfate, tartrate, thiocyanate,p-toluenesulfonate, undecanoate, valerate salts, and the like.

In other cases, the compounds of the present invention may contain oneor more acidic functional groups and, thus, are capable of formingpharmaceutically-acceptable salts with pharmaceutically-acceptablebases. The term “pharmaceutically-acceptable salts” in these instancesrefers to the relatively non-toxic, inorganic and organic base additionsalts of compounds of the present invention. These salts can likewise beprepared in situ in the administration vehicle or the dosage formmanufacturing process, or by separately reacting the purified compoundin its free acid form with a suitable base, such as the hydroxide,carbonate or bicarbonate of a pharmaceutically-acceptable metal cation,with ammonia, or with a pharmaceutically-acceptable organic primary,secondary, tertiary, or quaternary amine. Salts derived from appropriatebases include alkali metal, alkaline earth metal, ammonium andN⁺(C₁₋₄alkyl)₄ salts. Representative alkali or alkaline earth metalsalts include sodium, lithium, potassium, calcium, magnesium, and thelike. Further pharmaceutically acceptable salts include, whenappropriate, nontoxic ammonium, quaternary ammonium, and amine cationsformed using counterions such as halide, hydroxide, carboxylate,sulfate, phosphate, nitrate, loweralkyl sulfonate and aryl sulfonate.Representative organic amines useful for the formation of base additionsalts include ethylamine, diethylamine, ethylenediamine, ethanolamine,diethanolamine, piperazine and the like. (See, for example, Berge etal., supra).

Unless otherwise stated, structures depicted herein are also meant toinclude all isomeric (e.g., enantiomeric, diastereomeric, and geometric(or conformational)) forms of the structure; for example, the R and Sconfigurations for each stereocenter, Z and E double bond isomers, and Zand E conformational isomers. Therefore, single stereochemical isomersas well as enantiomeric, diastereomeric, and geometric (orconformational) mixtures of the present compounds are within the scopeof the invention. Unless otherwise stated, all tautomeric forms of thecompounds of the invention are within the scope of the invention.

If, for instance, a particular enantiomer of a compound of the presentinvention is desired, it may be prepared by asymmetric synthesis, chiralchromatography, or by derivation with a chiral auxiliary, where theresulting diastereomeric mixture is separated and the auxiliary groupcleaved to provide the pure desired enantiomers. Alternatively, wherethe molecule contains a basic functional group, such as amino, or anacidic functional group, such as carboxyl, diastereomeric salts areformed with an appropriate optically-active acid or base, followed byresolution of the diastereomers thus formed by fractionalcrystallization or chromatographic means well known in the art, andsubsequent recovery of the pure enantiomers.

Additionally, unless otherwise stated, structures depicted herein arealso meant to include compounds that differ only in the presence of oneor more isotopically enriched atoms. For example, compounds having thepresent structures including the replacement of hydrogen by deuterium ortritium, or the replacement of a carbon by a ¹³C- or ¹⁴C-enriched carbonare within the scope of this invention. Such compounds are useful, forexample, as analytical tools, as probes in biological assays, or astherapeutic agents in accordance with the present invention.

As described herein, compounds of the invention may contain “optionallysubstituted” moieties. In general, the term “substituted,” whetherpreceded by the term “optionally” or not, means that one or morehydrogens of the designated moiety are replaced with a suitablesubstituent. Unless otherwise indicated, an “optionally substituted”group may have a suitable substituent at each substitutable position ofthe group, and when more than one position in any given structure may besubstituted with more than one substituent selected from a specifiedgroup, the substituent may be either the same or different at everyposition. Combinations of substituents envisioned by this invention arepreferably those that result in the formation of stable or chemicallyfeasible compounds. The term “stable,” as used herein, refers tocompounds that are not substantially altered when subjected toconditions to allow for their production, detection, and, in certainembodiments, their recovery, purification, and use for one or more ofthe purposes disclosed herein.

Suitable monovalent substituents on a substitutable carbon atom of an“optionally substituted” group are independently halogen;—(CH₂)₀₋₄R^(∘); —(CH₂)₀₋₄OR^(∘); —O(CH₂)₀₋₄R^(∘), —O—(CH₂)₀₋₄C(O)OR^(∘);—(CH₂)₀₋₄CH(OR^(∘))₂; —(CH₂)₀₋₄SR^(∘); —(CH₂)₀₋₄Ph, which may besubstituted with R^(∘); —(CH₂)₀₋₄O(CH₂)₀₋₁Ph which may be substitutedwith R^(∘); —CH═CHPh, which may be substituted with R^(∘);—(CH₂)₀₋₄O(CH₂)₀₋₁-pyridyl which may be substituted with R^(∘); —NO₂;—CN; —N₃; —(CH₂)₀₋₄N(R^(∘))₂; —(CH₂)₀₋₄N(R^(∘))C(O)R^(∘);—N(R^(∘))C(S)R^(∘); —(CH₂)₀₋₄N(R^(∘))C(O)NR^(∘) ₂; —N(R^(∘))C(S)NR^(∘)₂; —(CH₂)₀₋₄N(R^(∘))C(O)OR^(∘); —N(R^(∘))N(R^(∘))C(O)R^(∘);—N(R^(∘))N(R^(∘))C(O)NR^(∘) ₂; —N(R^(∘))N(R^(∘))C(O)OR^(∘);—(CH₂)₀₋₄C(O)R^(∘); —C(S)R^(∘); —(CH₂)₀₋₄C(O)OR^(∘);—(CH₂)₀₋₄C(O)SR^(∘); —(CH₂)₀₋₄C(O)OSiR^(∘) ₃; —(CH₂)₀₋₄OC(O)R^(∘);—OC(O)(CH₂)₀₋₄SR—, SC(S)SR^(∘); —(CH₂)₀₋₄SC(O)R^(∘); —(CH₂)₀₋₄C(O)NR^(∘)₂; —C(S)NR^(∘) ₂; —C(S)SR^(∘); —SC(S)SR^(∘), —(CH₂)₀₋₄OC(O)NR^(∘) ₂;—C(O)N(OR^(∘))R^(∘); —C(O)C(O)R^(∘); —C(O)CH₂C(O)R^(∘);—C(NOR^(∘))R^(∘); —(CH₂)₀₋₄SSR^(∘); —(CH₂)₀₋₄S(O)₂R^(∘);—(CH₂)₀₋₄S(O)₂OR^(∘); —(CH₂)₀₋₄OS(O)₂R^(∘); —S(O)₂NR^(∘) ₂;—(CH₂)₀₋₄S(O)R^(∘); —N(R^(∘))S(O)₂NR^(∘) ₂; —N(R^(∘))S(O)₂R^(∘);—N(OR^(∘))R^(∘); —C(NH)NR^(∘) ₂; —P(O)₂R^(∘); —P(O)R^(∘) ₂; —OP(O)R^(∘)₂; —OP(O)(OR^(∘))₂; SiR^(∘) ₃; —(C₁₋₄ straight orbranched)alkylene)O—N(R^(∘))₂; or —(C₁₋₄ straight orbranched)alkylene)C(O)O—N(R^(∘))₂, wherein each R^(∘) may be substitutedas defined below and is independently hydrogen, C₁₋₆ aliphatic, —CH₂Ph,—O(CH₂)₀₋₁Ph, —CH₂-(5-6-membered heteroaryl ring), or a 5-6-memberedsaturated, partially unsaturated, or aryl ring having 0-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur, or,notwithstanding the definition above, two independent occurrences ofR^(∘), taken together with their intervening atom(s), form a3-12-membered saturated, partially unsaturated, or aryl mono- orbicyclic ring having 0-4 heteroatoms independently selected fromnitrogen, oxygen, or sulfur, which may be substituted as defined below.

Suitable monovalent substituents on R^(∘) (or the ring formed by takingtwo independent occurrences of R^(∘) together with their interveningatoms), are independently halogen, —(CH₂)₀₋₂R^(●), —(haloR^(●)),—(CH₂)₀₋₂OH, —(CH₂)₀₋₂OR^(●), —(CH₂)₀₋₂CH(OR^(●))₂; —O(haloR^(●)), —CN,—N₃, —(CH₂)₀₋₂C(O)R^(●), —(CH₂)₀₋₂C(O)OH, —(CH₂)₀₋₂C(O)OR^(●),—(CH₂)₀₋₂SR^(●), —(CH₂)₀₋₂SH, —(CH₂)₀₋₂NH₂, —(CH₂)₀₋₂NHR^(●),—(CH₂)₀₋₂NR^(●) ₂, —NO₂, —SiR^(●) ₃, —OSiR^(●) ₃, —C(O)SR^(●), —(C₁₋₄straight or branched alkylene)C(O)OR^(●), or —SSR^(●) wherein each R^(●)is unsubstituted or where preceded by “halo” is substituted only withone or more halogens, and is independently selected from C₁₋₄ aliphatic,—CH₂Ph, —O(CH₂)₀₋₁Ph, or a 5-6-membered saturated, partiallyunsaturated, or aryl ring having 0-4 heteroatoms independently selectedfrom nitrogen, oxygen, or sulfur. Suitable divalent substituents on asaturated carbon atom of R^(∘) include ═O and ═S.

Suitable divalent substituents on a saturated carbon atom of an“optionally substituted” group include the following: ═O, ═S, ═NNR*₂,═NNHC(O)R*, ═NNHC(O)OR*, ═NNHS(O)₂R*, ═NR*, ═NOR*, —O(C(R^(*) ₂))₂₋₃O—,or —S(C(R*₂))₂₋₃S—, wherein each independent occurrence of R* isselected from hydrogen, C₁₋₆ aliphatic which may be substituted asdefined below, or an unsubstituted 5-6-membered saturated, partiallyunsaturated, or aryl ring having 0-4 heteroatoms independently selectedfrom nitrogen, oxygen, or sulfur. Suitable divalent substituents thatare bound to vicinal substitutable carbons of an “optionallysubstituted” group include: —O(CR*₂)₂₋₃O—, wherein each independentoccurrence of R* is selected from hydrogen, C₁₋₆ aliphatic which may besubstituted as defined below, or an unsubstituted 5-6-memberedsaturated, partially unsaturated, or aryl ring having 0-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur.

Suitable substituents on the aliphatic group of R* include halogen,—R^(●), -(haloR^(●)), —OH, —OR^(●), —O(haloR^(●)), —CN, —C(O)OH,—C(O)OR^(●), —NH₂, —NHR^(●), —NR^(●) ₂, or —NO₂, wherein each R^(●) isunsubstituted or where preceded by “halo” is substituted only with oneor more halogens, and is independently C₁₋₄ aliphatic, —CH₂Ph,—O(CH₂)₀₋₁Ph, or a 5-6-membered saturated, partially unsaturated, oraryl ring having 0-4 heteroatoms independently selected from nitrogen,oxygen, or sulfur.

Suitable substituents on a substitutable nitrogen of an “optionallysubstituted” group include —R^(†), —NR^(†) ₂, —C(O)R^(†), —C(O)OR^(†),—C(O)C(O)R^(†), —C(O)CH₂C(O)R^(†), —S(O)₂R^(†), —S(O)₂NR^(†) ₂,—C(S)NR^(†) ₂, —C(NH)NR^(†) ₂, or —N(R^(†))S(O)₂R^(†); wherein eachR^(†) is independently hydrogen, C₁₋₆ aliphatic which may be substitutedas defined below, unsubstituted —OPh, or an unsubstituted 5-6-memberedsaturated, partially unsaturated, or aryl ring having 0-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur, or,notwithstanding the definition above, two independent occurrences ofR^(†), taken together with their intervening atom(s) form anunsubstituted 3-12-membered saturated, partially unsaturated, or arylmono- or bicyclic ring having 0-4 heteroatoms independently selectedfrom nitrogen, oxygen, or sulfur. Suitable substituents on the aliphaticgroup of R^(†) are independently halogen, —R^(●), -(haloR^(●)), —OH,—OR^(●), —O(haloR^(●)), —CN, —C(O)OH, —C(O)OR^(●), —NH₂, —NHR^(●),—NR^(●) ₂, or —NO₂, wherein each R^(●) is unsubstituted or wherepreceded by “halo” is substituted only with one or more halogens, and isindependently C₁₋₄ aliphatic, —CH₂Ph, —O(CH₂)₀₋₁Ph, or a 5-6-memberedsaturated, partially unsaturated, or aryl ring having 0-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur.

The term “multidrug resistant” as used herein refers to cells, celllines, cell states, tumors, neoplasms, cancers of a subject's body, andmicrobes that are resistant to a particular pharmaceutical agent. Suchmultidrug resistant cells and/or neoplasms may consist of mixedpopulations of malignant cells, some of which are drug-sensitive whileothers are drug-resistant. Chemotherapy may kill drug-sensitive cells,leaving behind a higher proportion of drug-resistant cells which maypropogate. Similarly, subpopulations of multidrug resistant microbes maysurvive chemotherapy and multiply, in some cases passing geneticinformation to neighboring microbes to confer resistance.

The phrases “parenteral administration” and “administered parenterally”as used herein means modes of administration other than enteral andtopical administration, usually by injection, and includes, withoutlimitation, intravenous, intramuscular, intraarterial, intrathecal,intracapsular, intraorbital, intracardiac, intradermal, intraperitoneal,transtracheal, subcutaneous, subcuticular, intraarticulare, subcapsular,subarachnoid, intraspinal and intrasternal injection and infusion.

The phrases “systemic administration,” “administered systemically,”“peripheral administration” and “administered peripherally” as usedherein mean the administration of a compound, drug or other materialother than directly into the central nervous system, such that it entersthe patient's system and, thus, is subject to metabolism and other likeprocesses, for example, subcutaneous administration.

Uses

Compounds of formulae I, III-A, III-B, III-C, or III-D may be used invitro or in vivo. The inventive compounds may be particularly useful inthe treatment of neoplasms or other proliferative diseases in vivo.However, inventive compounds described above may also be used in vitrofor research or clinical purposes (e.g., determining the susceptibilityof a patient's disease to a compound of formulae I, III-A, III-B, III-C,or III-D, researching the mechanism of action, elucidating a cellularpathway or process). In certain embodiments, the neoplasm is a benignneoplasm. In other embodiments, the neoplasm is a malignant neoplasm.Any cancer may be treated using compounds of formulae I, III-A, III-B,III-C, or III-D. Other proliferative diseases that may be treated usingcompounds of formulae I, III-A, III-B, III-C, or III-D includeinflammatory disease, autoimmune disease, diabetic retinopathy, andinfectious disease.

In certain embodiments, the malignancy is a hematological malignancy.Hematological malignancies are types of cancers that affect the blood,bone marrow, and/or lymph nodes. Examples of hematological malignanciesthat may be treated using compounds of formulae I, III-A, III-B, III-C,or III-D include, but are not limited to, acute lymphoblastic leukemia(ALL), acute myelogenous leukemia (AML), chronic myelogenous leukemia(CML), chronic lymphocytic leukemia (CLL), hairy cell leukemia,Hodgkin's lymphoma, non-Hodgkin's lymphoma, cutaneous T-cell lymphoma(CTCL), peripheral T-cell lymphoma (PTCL), Mantle cell lymphoma, B-celllymphoma, acute lymphoblastic T cell leukemia (T-ALL), acutepromyelocytic leukemia, and multiple myeloma. In certain embodiments,compounds of formulae I, III-A, III-B, III-C, or III-D are used to treatmultiple myeloma, glioblastoma, epithelial carcinoma, cervicaladenocarcinoma, or well-differentiated liposarcoma. In certainparticular embodiments, the cancer is relapsed and/or refractorymultiple myeloma. In other embodiments, compounds of formula I are usedto treat chromic lymphocytic leukemia (CLL). In certain embodiments,compounds of formulae I, III-A, III-B, III-C, or III-D are used to treatacute lymphoblastic leukemia (ALL). In certain embodiments, compounds offormulae I, III-A, III-B, III-C, or III-D are used to treat acutemyelogenous leukemia (AML). In certain embodiments, the cancer is achronic myeloid leukemia (CML). In certain embodiments, the cancer iscutaneous T-cell lymphoma. In other embodiments, the cancer isperipheral T-cell lymphoma. Compounds of formulae I, III-A, III-B,III-C, or III-D may also be used to treat a refractory or relapsedmalignancy. In certain embodiments, the cancer is a refractory and/orrelapsed hematological malignancy. In certain embodiments, the cancer ismultidrug resistant. For example, the cancer may be resistant to aparticular chemotherapeutic agent.

Other cancers besides hematological malignancies may also be treatedusing compounds of formulae I, III-A, III-B, III-C, or III-D. In certainembodiments, the cancer is a solid tumor. Exemplary cancers that may betreated using compounds of formulae I, III-A, III-B, III-C, or III-Dinclude colon cancer, lung cancer, bone cancer, pancreatic cancer,stomach cancer, esophageal cancer, skin cancer, brain cancer, livercancer, ovarian cancer, cervical cancer, uterine cancer, testicularcancer, prostate cancer, bladder cancer, kidney cancer, neuroendocrinecancer, breast cancer, gastric cancer, eye cancer, gallbladder cancer,laryngeal cancer, oral cancer, penile cancer, glandular tumors, rectalcancer, small intestine cancer, sarcoma, carcinoma, melanoma, urethralcancer, vaginal cancer, to name but a few. In certain embodiments,compounds of formulae I, III-A, III-B, III-C, or III-D are used to treatpancreatic cancer. In certain embodiments, compounds of formulae I,III-A, III-B, III-C, or III-D are used to treat prostate cancer. Incertain specific embodiments, the prostate cancer is hormone refractoryprostate cancer.

Compounds of formulae I, III-A, III-B, III-C, or III-D may also be usedto treat and/or kill cells in vitro. In certain embodiments, a cytotoxicconcentration of a compound of formulae I, III-A, III-B, III-C, or III-Dis contacted with the cells in order to kill them. In other embodiments,a sublethal concentration of a compound of formulae I, III-A, III-B,III-C, or III-D is used to treat the cells. In certain embodiments, theconcentration of a compound of formulae I, III-A, III-B, III-C, or III-Dranges from 0.01 nM to 100 nM. In certain embodiments, the concentrationof a compound of formulae I, III-A, III-B, III-C, or III-D ranges from0.1 nM to 50 nM. In certain embodiments, the concentration of a compoundof formulae I, III-A, III-B, III-C, or III-D ranges from 1 nM to 10 nM.In certain embodiments, the concentration of a compound of formulae I,III-A, III-B, III-C, or III-D ranges from 1 nM to 10 nM, moreparticularly 1 nM to 5 nM.

Any type of cell may be tested or killed with a compound of formulae I,III-A, III-B, III-C, or III-D. The cells may be derived from any animal,plant, bacterial, or fungal source. The cells may be at any stage ofdifferentiation or development. In certain embodiments, the cells areanimal cells. In certain embodiments, the cells are vertebrate cells. Incertain embodiments, the cells are mammalian cells. In certainembodiments, the cells are human cells. The cells may be derived from amale or female human in any stage of development. In certainembodiments, the cells are primate cells. In other embodiments, thecells are derived from a rodent (e.g., mouse, rat, guinea pig, hamster,gerbil). In certain embodiments, the cells are derived from adomesticated animal such as a dog, cat, cow, goat, pig, etc. The cellsmay also be derived from a genetically engineered animal or plant, suchas a transgenic mouse.

The cells used may be wild type or mutant cells. The cells may begenetically engineered. In certain embodiments, the cells are normalcells. In certain embodiments, the cells are hematological cells. Incertain embodiments, the cells are white blood cells. In certainparticular embodiments, the cells are precursors of white blood cells(e.g., stem cells, progenitor cells, blast cells). In certainembodiments, the cells are neoplastic cells. In certain embodiments, thecells are cancer cells. In certain embodiments, the cells are derivedfrom a hematological malignancy. In other embodiments, the cells arederived from a solid tumor. For example, the cells may be derived from apatient's tumor (e.g., from a biopsy or surgical excision). In certainembodiments, the cells are derived from a blood sample from the subjector from a bone marrow biopsy. In certain embodiments, the cells arederived from a lymph node biopsy. Such testing for cytotoxicity may beuseful in determining whether a patient's disease will respond to aparticular therapy. Such testing may also be useful in determining thedosage needed to treat the malignancy. This testing of thesusceptibility of a patient's cancer to a compound of formulae I, III-A,III-B, III-C, or III-D would prevent the unnecessary administration ofdrugs with no effect to the patient. The testing may also allow the useof lower dose of an inventive compound If the patient's cancer isparticularly susceptible to the compound.

In other embodiments, the cells are derived from cancer cells lines. Incertain embodiments, the cells are from hematological malignancies suchas those discussed herein. Human leukemia cell lines include U937,HL-60, HL-60/RV+ (a P-glycoprotein over-expressing multidrug resistantHL-60 variant which was selected by continuous exposure to the vincaalkaloid vincristine), THP-1, Raji, CCRF-CEM, ALL3 (acute lymphoblasticleukemia recently isolated from a patient treated at Memorial SloanKettering Cancer Center and characterized as Philadelphia chromosomepositive), and Jurkat. Exemplary CLL cell lines include JVM-3 and MEC-2.Exemplary myeloma cells lines include MM1.S, MM1.R(dexamethasone-resistant), RPMI8226, NCI-H929, and U266. Exemplarylymphoma cell lines include NCEB1 (Mantle cell lymphoma), JEKO (B celllymphoma), Karpas, SUDH-6, SUDH-16, L428, KMH2, and Granta mantlelymphoma cell line. In certain embodiments, the cells are AML cells ormultiple myeloma (CD138⁺) cells. In certain embodiments, the cells arehematopoietic stem or progenitor cells. For example, in certainembodiments, the cells are hematopoietic progenitor cells such as CD34⁺bone marrow cells. In certain embodiments, the cells are MOLT-3 (acutelymphoblastic T-cell), SKNLP (neuroblastoma), PC9 (adenocarcinoma),H1650 (adeocarcinoma), H1975 (adeocarcinoma), H2030 (adeocarcinoma),H3255 (adeocarcinoma), TC71 (Ewing's sarcoma), HTP-15 (glioblastoma),A431 (epithelial carcinoma), HeLa (cervical adenocarcinoma), or WD0082(well-differentiated liposarcoma) cells. In some embodiments, the cellsare HL-60/RV+ cells. In certain embodiments, the cell lines areresistant to a particular chemotherapeutic agent. In certain particularembodiments, the cell line is resistant to homoharringtonine.

In certain embodiments, compounds and pharmaceutical compositions of thepresent invention can be employed in combination therapies, that is, thecompounds and pharmaceutical compositions can be administeredconcurrently with, prior to, or subsequent to, one or more other desiredtherapeutics or medical procedures. The particular combination oftherapies (therapeutics or procedures) to employ in a combinationregimen will take into account compatibility of the desired therapeuticsand/or procedures and the desired therapeutic effect to be achieved. Itwill also be appreciated that the therapies employed may achieve adesired effect for the same disorder (for example, an inventive compoundmay be administered concurrently with another anticancer agent), or theymay achieve different effects (e.g., control of any adverse effects).

For example, other therapies or anticancer agents that may be used incombination with the inventive anticancer agents of the presentinvention include surgery, radiotherapy (γ-radiation, neutron beamradiotherapy, electron beam radiotherapy, proton therapy, brachytherapy,and systemic radioactive isotopes, to name a few), endocrine therapy,biologic response modifiers (interferons, interleukins, and tumornecrosis factor (TNF) to name a few), hyperthermia and cryotherapy,agents to attenuate any adverse effects (e.g., antiemetics), and otherapproved chemotherapeutic drugs, including, but not limited to,alkylating drugs (mechlorethamine, chlorambucil, Cyclophosphamide,Melphalan, Ifosfamide), antimetabolites (Methotrexate), purineantagonists and pyrimidine antagonists (6-Mercaptopurine,5-Fluorouracil, Cytarabile, Gemcitabine), spindle poisons (Vinblastine,Vincristine, Vinorelbine, Paclitaxel), podophyllotoxins (Etoposide,Irinotecan, Topotecan), antibiotics (Doxorubicin, Bleomycin, Mitomycin),nitrosoureas (Carmustine, Lomustine), inorganic ions (Cisplatin,Carboplatin), enzymes (Asparaginase), and hormones (Tamoxifen,Leuprolide, Flutamide, and Megestrol), to name a few. Additionally, thepresent invention also encompasses the use of certain cytotoxic oranticancer agents currently in clinical trials and which may ultimatelybe approved by the FDA (including, but not limited to, epothilones andanalogues thereof and geldanamycins and analogues thereof). For a morecomprehensive discussion of updated cancer therapies see,http://www.nci.nih.gov/, a list of the FDA approved oncology drugs athttp://www.fda.gov/cder/cancer/druglistframe.htm, and The Merck Manual,Seventeenth Ed. 1999, the entire contents of which are herebyincorporated by reference.

In certain embodiments, inventive compounds are useful in treating asubject in clinical remission, where the subject has been treated bysurgery or has limited unresected disease.

In certain embodiments, inventive compounds are useful in treatingmultidrug resistant cancer. In some embodiments, such compounds areselected from:

It will be appreciated that, as natural products, cephalotaxus estersmay possess antimicrobial activity. In certain embodiments, compounds offormulae I, III-A, III-B, III-C, or III-D are useful in treatingmicrobial infection. In some embodiments, compounds of formulae I,III-A, III-B, III-C, or III-D induce antimicrobial activity in a subjectwith a pathological microbe infection. In certain embodiments, thesubject is an animal. In certain embodiments, the subject is human. Insome embodiments, compounds of formulae I, III-A, III-B, III-C, or III-Dinduce antimicrobial in cells of a biological sample. In certainembodiments, the microbe is bacterial. In certain embodiments, themicrobe is fungal.

In another aspect, the invention provides a method of treatinginfectious disease in a subject comprising administering to the subjecta therapeutically effective amount of a compound of formulae I, III-A,III-B, III-C, or III-D. In some embodiments, the subject is human. Incertain embodiments, the infection is caused by a bacterium. In certainembodiments, the infection is caused by a fungus. In certainembodiments, the infection is caused by a parasite.

Formulations

Inventive compounds may be combined with a pharmaceutically acceptableexcipient to form a pharmaceutical composition. In certain embodiments,the pharmaceutical composition includes a pharmaceutically acceptableamount of an inventive compound. The amount of active ingredient whichcan be combined with a carrier material to produce a single dosage formwill vary depending upon the host being treated, and the particular modeof administration. The amount of active ingredient that can be combinedwith a carrier material to produce a single dosage form will generallybe that amount of the compound which produces a therapeutic effect.Generally, this amount will range from about 1% to about 99% of activeingredient, preferably from about 5% to about 70%, most preferably fromabout 10% to about 30%.

Wetting agents, emulsifiers and lubricants, such as sodium laurylsulfate and magnesium stearate, as well as coloring agents, releaseagents, coating agents, sweetening, flavoring and perfuming agents,preservatives and antioxidants can also be present in the compositions.

Examples of pharmaceutically-acceptable antioxidants include: watersoluble antioxidants, such as ascorbic acid, cysteine hydrochloride,sodium bisulfate, sodium metabisulfite, sodium sulfite and the like;oil-soluble antioxidants, such as ascorbyl palmitate, butylatedhydroxyanisole (BHA), butylated hydroxytoluene (BHT), lecithin, propylgallate, alpha-tocopherol, and the like; and metal chelating agents,such as citric acid, ethylenediamine tetraacetic acid (EDTA), sorbitol,tartaric acid, phosphoric acid, and the like.

Formulations of the present invention include those suitable for oral,nasal, topical (including buccal and sublingual), rectal, vaginal and/orparenteral administration. The formulations may conveniently bepresented in unit dosage form and may be prepared by any methods wellknown in the art of pharmacy. In certain embodiments, a formulation ofthe present invention comprises an excipient selected from the groupconsisting of cyclodextrins, liposomes, micelle forming agents, e.g.,bile acids, and polymeric carriers, e.g., polyesters and polyanhydrides;and a compound of the present invention. In certain embodiments, anaforementioned formulation renders orally bioavailable a compound of thepresent invention.

Methods of preparing these formulations or compositions include the stepof bringing into association a compound of the present invention withthe carrier and, optionally, one or more accessory ingredients. Ingeneral, the formulations are prepared by uniformly and intimatelybringing into association a compound of the present invention withliquid carriers, or finely divided solid carriers, or both, and then, ifnecessary, shaping the product.

Formulations of the invention suitable for oral administration may be inthe form of capsules, cachets, pills, tablets, lozenges (using aflavored basis, usually sucrose and acacia or tragacanth), powders,granules, or as a solution or a suspension in an aqueous or non-aqueousliquid, or as an oil-in-water or water-in-oil liquid emulsion, or as anelixir or syrup, or as pastilles (using an inert base, such as gelatinand glycerin, or sucrose and acacia) and/or as mouth washes and thelike, each containing a predetermined amount of a compound of thepresent invention as an active ingredient. A compound of the presentinvention may also be administered as a bolus, electuary or paste.

In solid dosage forms of the invention for oral administration(capsules, tablets, pills, dragees, powders, granules and the like), theactive ingredient is mixed with one or more pharmaceutically-acceptablecarriers, such as sodium citrate or dicalcium phosphate, and/or any ofthe following: fillers or extenders, such as starches, lactose, sucrose,glucose, mannitol, and/or silicic acid; binders, such as, for example,carboxymethylcellulose, alginates, gelatin, polyvinyl pyrrolidone,sucrose and/or acacia; humectants, such as glycerol; disintegratingagents, such as agar-agar, calcium carbonate, potato or tapioca starch,alginic acid, certain silicates, and sodium carbonate; solutionretarding agents, such as paraffin; absorption accelerators, such asquaternary ammonium compounds; wetting agents, such as, for example,cetyl alcohol, glycerol monostearate, and non-ionic surfactants;absorbents, such as kaolin and bentonite clay; lubricants, such as talc,calcium stearate, magnesium stearate, solid polyethylene glycols, sodiumlauryl sulfate, and mixtures thereof; and coloring agents. In the caseof capsules, tablets and pills, the pharmaceutical compositions may alsocomprise buffering agents. Solid compositions of a similar type may alsobe employed as fillers in soft and hard-shelled gelatin capsules usingsuch excipients as lactose or milk sugars, as well as high molecularweight polyethylene glycols and the like.

A tablet may be made by compression or molding, optionally with one ormore accessory ingredients. Compressed tablets may be prepared usingbinder (for example, gelatin or hydroxypropylmethyl cellulose),lubricant, inert diluent, preservative, disintegrant (for example,sodium starch glycolate or cross-linked sodium carboxymethyl cellulose),surface-active or dispersing agent. Molded tablets may be made in asuitable machine in which a mixture of the powdered compound ismoistened with an inert liquid diluent.

The tablets, and other solid dosage forms of the pharmaceuticalcompositions of the present invention, such as dragees, capsules, pillsand granules, may optionally be scored or prepared with coatings andshells, such as enteric coatings and other coatings well known in thepharmaceutical-formulating art. They may also be formulated so as toprovide slow or controlled release of the active ingredient thereinusing, for example, hydroxypropylmethyl cellulose in varying proportionsto provide the desired release profile, other polymer matrices,liposomes and/or microspheres. They may be formulated for rapid release,e.g., freeze-dried. They may be sterilized by, for example, filtrationthrough a bacteria-retaining filter, or by incorporating sterilizingagents in the form of sterile solid compositions that can be dissolvedin sterile water, or some other sterile injectable medium immediatelybefore use. These compositions may also optionally contain opacifyingagents and may be of a composition that they release the activeingredient(s) only, or preferentially, in a certain portion of thegastrointestinal tract, optionally, in a delayed manner. Examples ofembedding compositions that can be used include polymeric substances andwaxes. The active ingredient can also be in micro-encapsulated form, ifappropriate, with one or more of the above-described excipients.

Liquid dosage forms for oral administration of the compounds of theinvention include pharmaceutically acceptable emulsions, microemulsions,solutions, suspensions, syrups and elixirs. In addition to the activeingredient, the liquid dosage forms may contain inert diluents commonlyused in the art, such as, for example, water or other solvents,solubilizing agents and emulsifiers, such as ethyl alcohol, isopropylalcohol, ethyl carbonate, ethyl acetate, benzyl alcohol, benzylbenzoate, propylene glycol, 1,3-butylene glycol, oils (in particular,cottonseed, groundnut, corn, germ, olive, castor and sesame oils),glycerol, tetrahydrofuryl alcohol, polyethylene glycols and fatty acidesters of sorbitan, and mixtures thereof.

Besides inert diluents, the oral compositions can also include adjuvantssuch as wetting agents, emulsifying and suspending agents, sweetening,flavoring, coloring, perfuming and preservative agents.

Suspensions, in addition to the active compounds, may contain suspendingagents as, for example, ethoxylated isostearyl alcohols, polyoxyethylenesorbitol and sorbitan esters, microcrystalline cellulose, aluminummetahydroxide, bentonite, agar-agar and tragacanth, and mixturesthereof.

Formulations of the pharmaceutical compositions of the invention forrectal or vaginal administration may be presented as a suppository,which may be prepared by mixing one or more compounds of the inventionwith one or more suitable nonirritating excipients or carrierscomprising, for example, cocoa butter, polyethylene glycol, asuppository wax or a salicylate, and which is solid at room temperature,but liquid at body temperature and, therefore, will melt in the rectumor vaginal cavity and release the active compound.

Formulations of the present invention which are suitable for vaginaladministration also include pessaries, tampons, creams, gels, pastes,foams or spray formulations containing such carriers as are known in theart to be appropriate.

Dosage forms for the topical or transdermal administration of a compoundof this invention include powders, sprays, ointments, pastes, creams,lotions, gels, solutions, patches and inhalants. The active compound maybe mixed under sterile conditions with a pharmaceutically-acceptablecarrier, and with any preservatives, buffers, or propellants which maybe required.

The ointments, pastes, creams and gels may contain, in addition to anactive compound of this invention, excipients, such as animal andvegetable fats, oils, waxes, paraffins, starch, tragacanth, cellulosederivatives, polyethylene glycols, silicones, bentonites, silicic acid,talc and zinc oxide, or mixtures thereof.

Powders and sprays can contain, in addition to a compound of thisinvention, excipients such as lactose, talc, silicic acid, aluminumhydroxide, calcium silicates and polyamide powder, or mixtures of thesesubstances. Sprays can additionally contain customary propellants, suchas chlorofluorohydrocarbons and volatile unsubstituted hydrocarbons,such as butane and propane.

Transdermal patches have the added advantage of providing controlleddelivery of a compound of the present invention to the body. Dissolvingor dispersing the compound in the proper medium can make such dosageforms. Absorption enhancers can also be used to increase the flux of thecompound across the skin. Either providing a rate controlling membraneor dispersing the compound in a polymer matrix or gel can control therate of such flux.

Ophthalmic formulations, eye ointments, powders, solutions and the like,are also contemplated as being within the scope of this invention.

Pharmaceutical compositions of this invention suitable for parenteraladministration comprise one or more compounds of the invention incombination with one or more pharmaceutically-acceptable sterileisotonic aqueous or nonaqueous solutions, dispersions, suspensions oremulsions, or sterile powders which may be reconstituted into sterileinjectable solutions or dispersions just prior to use, which may containsugars, alcohols, antioxidants, buffers, bacteriostats, solutes whichrender the formulation isotonic with the blood of the intended recipientor suspending or thickening agents.

Examples of suitable aqueous and nonaqueous carriers, which may beemployed in the pharmaceutical compositions of the invention includewater, ethanol, polyols (such as glycerol, propylene glycol,polyethylene glycol, and the like), and suitable mixtures thereof,vegetable oils, such as olive oil, and injectable organic esters, suchas ethyl oleate. Proper fluidity can be maintained, for example, by theuse of coating materials, such as lecithin, by the maintenance of therequired particle size in the case of dispersions, and by the use ofsurfactants.

These compositions may also contain adjuvants such as preservatives,wetting agents, emulsifying agents and dispersing agents. Prevention ofthe action of microorganisms upon the subject compounds may be ensuredby the inclusion of various antibacterial and antifungal agents, forexample, paraben, chlorobutanol, phenol sorbic acid, and the like. Itmay also be desirable to include isotonic agents, such as sugars, sodiumchloride, and the like into the compositions. In addition, prolongedabsorption of the injectable pharmaceutical form may be brought about bythe inclusion of agents which delay absorption such as aluminummonostearate and gelatin.

In some cases, in order to prolong the effect of a drug, it is desirableto slow the absorption of the drug from subcutaneous or intramuscularinjection. This may be accomplished by the use of a liquid suspension ofcrystalline or amorphous material having poor water solubility. The rateof absorption of the drug then depends upon its rate of dissolution,which in turn, may depend upon crystal size and crystalline form.Alternatively, delayed absorption of a parenterally-administered drugform is accomplished by dissolving or suspending the drug in an oilvehicle.

Injectable depot forms are made by forming microencapsule matrices ofthe subject compounds in biodegradable polymers such aspolylactide-polyglycolide. Depending on the ratio of drug to polymer,and the nature of the particular polymer employed, the rate of drugrelease can be controlled. Examples of other biodegradable polymersinclude poly(orthoesters) and poly(anhydrides). Depot injectableformulations are also prepared by entrapping the drug in liposomes ormicroemulsions, which are compatible with body tissue.

In certain embodiments, a compound or pharmaceutical preparation isadministered orally. In other embodiments, the compound orpharmaceutical preparation is administered intravenously. Alternativerouts of administration include sublingual, intramuscular, andtransdermal administrations.

When the compounds of the present invention are administered aspharmaceuticals, to humans and animals, they can be given per se or as apharmaceutical composition containing, for example, 0.1% to 99.5% (morepreferably, 0.5% to 90%) of active ingredient in combination with apharmaceutically acceptable carrier.

The preparations of the present invention may be given orally,parenterally, topically, or rectally. They are of course given in formssuitable for each administration route. For example, they areadministered in tablets or capsule form, by injection, inhalation, eyelotion, ointment, suppository, etc. administration by injection,infusion or inhalation; topical by lotion or ointment; and rectal bysuppositories. Oral administrations are preferred.

These compounds may be administered to humans and other animals fortherapy by any suitable route of administration, including orally,nasally, as by, for example, a spray, rectally, intravaginally,parenterally, intracisternally and topically, as by powders, ointmentsor drops, including buccally and sublingually.

Regardless of the route of administration selected, the compounds of thepresent invention, which may be used in a suitable hydrated form, and/orthe pharmaceutical compositions of the present invention, are formulatedinto pharmaceutically-acceptable dosage forms by conventional methodsknown to those of skill in the art.

Actual dosage levels of the active ingredients in the pharmaceuticalcompositions of this invention may be varied so as to obtain an amountof the active ingredient that is effective to achieve the desiredtherapeutic response for a particular patient, composition, and mode ofadministration, without being toxic to the patient.

The selected dosage level will depend upon a variety of factorsincluding the activity of the particular compound of the presentinvention employed, or the ester, salt or amide thereof, the route ofadministration, the time of administration, the rate of excretion ormetabolism of the particular compound being employed, the duration ofthe treatment, other drugs, compounds and/or materials used incombination with the particular compound employed, the age, sex, weight,condition, general health and prior medical history of the patient beingtreated, and like factors well known in the medical arts.

A physician or veterinarian having ordinary skill in the art can readilydetermine and prescribe the effective amount of the pharmaceuticalcomposition required. For example, the physician or veterinarian couldstart doses of the compounds of the invention employed in thepharmaceutical composition at levels lower than that required to achievethe desired therapeutic effect and then gradually increasing the dosageuntil the desired effect is achieved.

In some embodiments, a compound or pharmaceutical composition of theinvention is provided to a subject chronically. Chronic treatmentsinclude any form of repeated administration for an extended period oftime, such as repeated administrations for one or more months, between amonth and a year, one or more years, or longer. In many embodiments, achronic treatment involves administering a compound or pharmaceuticalcomposition of the invention repeatedly over the life of the subject.Preferred chronic treatments involve regular administrations, forexample one or more times a day, one or more times a week, or one ormore times a month. In general, a suitable dose such as a daily dose ofa compound of the invention will be that amount of the compound that isthe lowest dose effective to produce a therapeutic effect. Such aneffective dose will generally depend upon the factors described above.Generally doses of the compounds of this invention for a patient, whenused for the indicated effects, will range from about 0.0001 to about100 mg per kg of body weight per day. Preferably the daily dosage willrange from 0.001 to 50 mg of compound per kg of body weight, and evenmore preferably from 0.01 to 10 mg of compound per kg of body weight.However, lower or higher doses can be used. In some embodiments, thedose administered to a subject may be modified as the physiology of thesubject changes due to age, disease progression, weight, or otherfactors.

If desired, the effective daily dose of the active compound may beadministered as two, three, four, five, six or more sub-dosesadministered separately at appropriate intervals throughout the day,optionally, in unit dosage forms.

While it is possible for a compound of the present invention to beadministered alone, it is preferable to administer the compound as apharmaceutical formulation (composition) as described above.

The compounds according to the invention may be formulated foradministration in any convenient way for use in human or veterinarymedicine, by analogy with other pharmaceuticals.

The invention provides kits comprising pharmaceutical compositions of aninventive compound. In certain embodiments, such kits including thecombination of a compound of formulae I, III-A, III-B, III-C, or III-Dand another chemotherapeutic agent. The agents may be packagedseparately or together. The kit optionally includes instructions forprescribing the medication. In certain embodiments, the kit includesmultiple doses of each agent. The kit may include sufficient quantitiesof each component to treat a subject for a week, two weeks, three weeks,four weeks, or multiple months. The kit may include a full cycle ofchemotherapy. In certain embodiments, the kit includes multiple cyclesof chemotherapy.

The entire contents of all references cited above and herein are herebyincorporated by reference.

The foregoing written specification is considered to be sufficient toenable one skilled in the art to practice the invention. The presentinvention is not to be limited in scope by examples provided, since theexamples are intended as a single illustration of one aspect of theinvention and other functionally equivalent embodiments are within thescope of the invention. Various modifications of the invention inaddition to those shown and described herein will become apparent tothose skilled in the art from the foregoing description and fall withinthe scope of the appended claims. The advantages and objects of theinvention are not necessarily encompassed by each embodiment of theinvention.

EXEMPLIFICATION

Unless otherwise noted, operations related to synthetic chemistry werecarried out as described under general procedures.

General Procedures.

All reactions were performed in flame-dried modified Schlenk (Kjeldahlshape) flasks fitted with a glass stopper under a positive pressure ofargon, unless otherwise noted. Air- and moisture-sensitive liquids andsolutions were transferred via syringe. Organic solutions wereconcentrated by rotary evaporation below 30° C. Flash columnchromatography was performed employing 230-400 mesh silica gel.Thin-layer chromatography (analytical and preparative) was performedusing glass plates pre-coated to a depth of 0.25 mm with 230-400 meshsilica gel impregnated with a fluorescent indicator (254 nm).

Materials

Dichloromethane (DCM), tetrahydrofuran (THF), acetonitrile, diethylether, hexane, toluene, and benzene were purified by passage through twopacked columns of neutral alumina under an argon atmosphere. Methanolwas distilled from magnesium at 760 Torr. Dimethylformamide (DMF),isopropanol (IPA), and ethanol were dried over 4 Å molecular sieves.Trifluoromethanesulfonic anhydride (Tf₂O) was distilled from phosphoruspentoxide at 760 Torr.

Instrumentation

Infrared (IR) spectra were obtained using a Perkin Elmer Spectrum BXspectrophotometer or a Bruker Tensor 27 referenced to a polystyrenestandard. Data are presented as the frequency of absorption (cm⁻¹).Proton and carbon-13 nuclear magnetic resonance (¹H NMR or ¹³C NMR)spectra were recorded on a Varian 400, a Varian 500, Varian Inova 500NMR, or a Bruker Avance III spectrometer; chemical shifts are expressedin parts per million (δ scale) downfield from tetramethylsilane and arereferenced to the residual protium in the NMR solvent (CHCl₃: δ 7.26 for¹H NMR, δ 77.16 for ¹³C NMR; CD₃OD: δ 3.30 for ¹H NMR, δ 49.00 for ¹³CNMR). Data are presented as follows: chemical shift, multiplicity(s=singlet, bs=broad singlet, d=doublet, bd=broad doublet, t=triplet,m=multiplet and/or multiple resonances), coupling constant in Hertz(Hz), integration, assignment.

Example 1

Alcoholic extracts of the powdered leaves and stems of Cephalotaxusgenera yield cephalotaxine (1, FIG. 1) as the most abundant alkaloidconstituent, (L. Huang and Z. Xue, Alkaloids 1984, 23, 157-226; W. W.Paudler, J. McKay and G. I. Kerley, J. Org. Chem. 1963, 28, 2194) whosestructure was unambiguously verified by X-ray crystallographic analysis.(R. G. Powell, Weislede. D, C. R. Smith and I. A. Wolff, TetrahedronLett. 1969, 4081; D. J. Abraham, Rosenste. Rd and E. L. McGandy,Tetrahedron Lett. 1969, 4085; S. K. Arora, R. B. Bates and R. A. Grady,J. Org. Chem. 1974, 39, 1269-1271; S. K. Arora, R. B. Bates, R. A.Grady, G. Germain, J. P. Declercq and R. G. Powell, J. Org. Chem. 1976,41, 551-554) While cephalotaxine (1) accounts for approximately 50% ofthe mass of the crude alkaloid extract mixture, many minor constituentshave also been identified. Among these are several rare C3-esterderivatives, including complex variants such as deoxyharringtonine (2)(K. L. Mikolajczak, C. R. Smith and R. G. Powell, Tetrahedron 1972, 28,1995), homoharringtonine (3) (R. G. Powell, D. Weisleder, C. R. Smith,Jr. and W. K. Rohwedder, Tetrahedron Lett. 1970, 815-818),homodeoxyharringtonine (4) (I. Takano, I. Yasuda, M. Nishijima, Y.Hitotsuyanagi, K. Takeya and H. Itokawa, J. Nat. Prod. 1996, 59,965-967), and anhydroharringtonine (5) (D. Z. Wang, G. E. Ma and R. S.Xu, Acta pharmaceutica Sinica 1992, 27, 173-177).

Early biological evaluations of these alkaloids revealed that severalCephalotaxus esters demonstrate acute toxicity toward various murineleukemia, murine lymphoma, and human epidermoid carcinoma cells. (H.Morita, M. Arisaka, N. Yoshida and J. Kobayashi, Tetrahedron 2000, 56,2929-2934; Powell, et al., supra) Deoxyharringtonine (2),homoharringtonine (3), and homodeoxyharringtonine (4) exhibit IC₅₀levels of 7.5, 17, and 56 ng/mL, respectively, against P388 leukemiacells. Likewise, anhydroharringtonine (5) was reported to induce 98%growth inhibition of P388 leukemia cells at 1 μg/mL, a level comparableto that of deoxyharringtonine (2). (D. Z. Wang, G. E. Ma and R. S. Xu,Acta pharmaceutica Sinica 1992, 27, 178-184) By contrast, cephalotaxine(1) itself was found to be biologically inactive. (M. A. J. Miah, T.Hudlicky and J. W. Reed, Alkaloids 1998, 51, 199-269) The cytotoxicproperties of the cephalotaxus esters arise from reversible inhibitionof protein synthesis (M. T. Huang, Mol. Pharmacol. 1975, 11, 511-519)via induction of rapid breakdown of the polyribosome, with concomitantrelease of the polypeptide chain. (M. Fresno, A. Jimenez and D. Vazquez,Eur. J. Biochem. 1977, 72, 323-330) The remarkable anti-leukemiaactivity of several Cephalotaxus esters spawned intense investigationsinto their therapeutic potential. Clinical studies were first performedin the mid-1970s in China, where the seeds of Cephalotaxus plants hadlong been used in traditional medicine. These results prompted Phase Iclinical evaluation of homoharringtonine (3) in the US in 1981, (S. S.Legha, M. Keating, S. Picket, J. A. Ajani, M. Ewer and G. P. Bodey,Cancer Treatment Reports 1984, 68, 1085-1091) advancing to more recentPhase II studies. (H. M. Kantarjian, M. Talpaz, V. Santini, A. Murgo, B.Cheson and S. M. O'Brien, Cancer 2001, 92, 1591-1605) While difficultiesin production, coupled with its hematologic toxicity and susceptibilityto multidrug resistance (MDR), (Z. Benderra, H. Morjani, A. Trussardiand M. Manfait, Leukemia 1998, 12, 1539-1544) have hindered thedevelopment of 3, it is still viewed as a useful drug for the treatmentof chronic myeloid leukemia in combination therapy. (Kantarjian, et al.,supra)

Cephalotaxine (1) has received considerable and enduring attention inthe arena of total synthesis. Several elegant syntheses of 1 have beenreported over the past three decades. The racemic approaches haveembodied several key transformations, including Nazarov cyclization, (J.Auerbach and S. M. Weinreb, J. Am. Chem. Soc. 1972, 94, 7172)photo-stimulated S_(RN)1 cyclization, (M. F. Semmelhack, B. P. Chong, R.D. Stauffer, T. D. Rogerson, A. Chong and L. D. Jones, J. Am. Chem. Soc.1975, 97, 2507-2516) Claisen rearrangement, (S. Yasuda, T. Yamada and M.Hanaoka, Tetrahedron Lett. 1986, 27, 2023-2026; S. Yasuda, Y. Yamamoto,S. Yoshida and M. Hanaoka, Chem. Pharm. Bull. 1988, 36, 4229-4231)oxidative ring contraction, (M. E. Kuehne, W. G. Bornmann, W. H.Parsons, T. D. Spitzer, J. F. Blount and J. Zubieta, J. Org. Chem. 1988,53, 3439-3450) acyInitroso Diels-Alder cycloaddition, (T. P. Burkholderand P. L. Fuchs, J. Am. Chem. Soc. 1988, 110, 2341-2342; T. P.Burkholder and P. L. Fuchs, J. Am. Chem. Soc. 1990, 112, 9601-9613)trans-annular N-conjugate addition, (X. D. Lin, R. W. Kavash and P. S.Mariano, J. Am. Chem. Soc. 1994, 116, 9791-9792; X. D. Lin, R. W. Kavashand P. S. Mariano, J. Org. Chem. 1996, 61, 7335-7347) intramolecularalkyne hydroamination, (Y. Koseki, H. Sato, Y. Watanabe and T. Nagasaka,Org. Lett. 2002, 4, 885-888) and reductive ring expansion oftetrahydrosioquinoline intermediates. (W. D. Z. Li and Y. Q. Wang, Org.Lett. 2003, 5, 2931-2934; W. D. Z. Li and B. C. Ma, J. Org. Chem. 2005,70, 3277-3280) Non-racemic routes have featured electrophilic aromaticsubstitution, (N. Isono and M. Mori, J. Org. Chem. 1995, 60, 115-119)Heck arylation, (L. F. Tietze and H. Schirok, Angew. Chem. Int. Ed.1997, 36, 1124-1125; L. F. Tietze and H. Schirok, J. Am. Chem. Soc.1999, 121, 10264-10269) Pummerer-electrophilic aromatic substitutioncascade, (H. Ishibashi, M. Okano, H. Tamaki, K. Maruyama, T. Yakura andM. Ikeda, J. Chem. Soc., Chem. Commun. 1990, 1436-1437; M. Ikeda, M.Okano, K. Kosaka, M. Kido and H. Ishibashi, Chem. Pharm. Bull. 1993, 41,276-281; M. Ikeda, S. A. A. El Bialy, K. Hirose, M. Kotake, T. Sato, S.M. M. Bayomi, I. A. Shehata, A. M. Abdelal, L. M. Gad and T. Yakura,Chem. Pharm. Bull. 1999, 47, 983-987) and acid catalyzed ring expansionof cyclobutanol derivatives. (L. Planas, J. Perard-Viret and J. Royer,J. Org. Chem. 2004, 69, 3087-3092)

On the other hand, the significance of the complex cephalotaxus esters(e.g., 2-5) extends beyond that of 1 on several levels, the mostprominent of which being their exceedingly potent anti-proliferativeproperties. Moreover, the scarcity of these complex ester derivativesfrom the natural source is far more pronounced than that of 1, whereincomplex cephalotaxus esters are typically attainable in only <0.1% ofthe plant dry weight. Thus, a goal in the work described herein was theestablishment of a synthetic approach to the bioactive cephalotaxusesters by a route completely distinct from previous efforts. (J. D.Eckelbarger, J. T. Wilmot and D. Y. Gin, J. Am. Chem. Soc. 2006, 128,10370-10371) Several key elements in the synthetic strategy include(FIG. 6): (1) introduction of the nitrogen atom via Neber rearrangement;(2) construction of the benzazepine core via the strain-releaserearrangement of N-vinyl-2-aryl aziridines; (3) assembly of thespiro-fused pyrrolidine core via 1,3-dipolar cycloaddition of azomethineylides derived from vinylogous amides; and (4) synthesis of strainedvariants of advanced side chain intermediates to facilitate late-stagecephalotaxine acylation. Notably, the latter three elements had not beenapplied to complex natural product synthesis, yet ultimately playedcritical roles in the non-racemic syntheses of the cephalotaxus esters2-5.

The success of the synthetic endeavors described herein enabledextensive cytotoxicity evaluation of several advanced natural andnon-natural compounds with an array of well established humanhematopoietic and solid tumor cell lines. Potent cytotoxicity wasobserved in several cell lines previously not challenged with thesealkaloids. Moreover, comparative cytotoxicity assays reveal thepotential of synthetic structural modification of this family ofalkaloids to modulate susceptibility to multi-drug resistance.

Results and Discussion

Dihydro[3]Benzazepine Construction Via Strain-Release Rearrangement. Thefirst challenge addressed in the synthesis of cephalotaxine (1) focusedon construction of its seven-membered N-heterocycle. Strain-release[3,3]-sigmatropic rearrangements, in which a high energy three-memberedring is incorporated into the 1,5-diene system of the substrate, havebeen widely used for the construction of 7-membered rings. Although theall-carbon divinyl cyclopropane rearrangement has received the mostattention, the heterocyclic epoxide-, thiirane-, andaziridine-containing variants are also documented. (T. Hudlicky, R. Fan,J. W. Reed and K. G. Gadamasetti, Org. React. 1992, 41, 1-133) However,the aziridine-to-azepine version of this transformation (W. Lwowski, T.J. Maricich and T. W. Mattingly, Jr., J. Am. Chem. Soc. 1963, 85,1200-1202; E. L. Stogryn and S. J. Brois, J. Org. Chem. 1965, 30, 88; J.C. Pommelet and J. Chuche, Tetrahedron Lett. 1974, 3897-3898; M. Zora,J. Org. Chem. 2005, 70, 6018-6026; A. Hassner, R. Dcosta, A. T. McPhailand W. Butler, Tetrahedron Lett. 1981, 22, 3691-3694; L. Viallon, O.Reinaud, P. Capdevielle and M. Maumy, Tetrahedron Lett. 1995, 36,4787-4790; U. M. Lindstrom and P. Somfai, J. Am. Chem. Soc. 1997, 119,8385-8386) has only been sporadically used in target-directed synthesis.In this context, adaptation to the synthesis of benzazepines andheterocyclic variants thereof have focused on N-aryl-2-vinyl aziridinesto form dihydro[1]benzazepines. (P. Scheiner, J. Org. Chem. 1967, 32,2628; H. P. Figeys and R. Jammar, Tetrahedron Lett. 1980, 21, 2995-2998;H. P. Figeys and R. Jammar, Tetrahedron Lett. 1981, 22, 637-640)

However, the [3,3]-sigmatropic rearrangement of N-vinyl-2-arylaziridines to form dihydro[3]benzazepines, such as that present in 1,had not been reported. Thus, investigations into this reaction commencedwith the synthesis of a few N-vinyl-2-aryl aziridines (Scheme 1-1) viathe condensation of acetophenone derivatives 7/8/9 with hydroxylaminehydrochloride to provide the corresponding oximes (10/11/12) in highyields (95%/95%/87%), respectively. (T. Harada, T. Ohno, S. Kobayashiand T. Mukaiyama, Synthesis 1991, 1216-1220) Each of these oximes wasexposed to LiAlH₄ and i-Pr₂NH at elevated temperatures to inducereductive Neber rearrangement, (H. Tanida, T. Okada and K. Kotera, Bull.Chem. Soc. Jpn. 1973, 46, 934-938) furnishing the correspondingaziridines (13/14/15) in good yields (76%/74%/88%), and providing aseries of substituted 2-aryl aziridines available for N-vinylation. Thiswas most conveniently accomplished via addition-elimination with thereadily available alkene electrophile 3-chloro-2-cyclopentenone (16),prepared in one step from the reaction of 1,3-cyclopentanedione withoxalyl chloride. (J. W. Ullrich, F. T. Chiu, T. Tinerharding and P. S.Mariano, J. Org. Chem. 1984, 49, 220-228) Condensation of the twosubstrates 13 and 16 with expulsion of HCl provided the vinyl aziridine17 in moderate yield (58%). By comparison, coupling of aziridine 14 or15 with chloroenone 16 proceeded with significantly diminishedefficiency, resulting in only a 16% and 26% isolated yield of vinylaziridines 18 and 19, respectively.

Nevertheless, access to these three 2-aryl-N-vinyl aziridines 17-19allowed for investigations into the feasibility of the ring expansionrearrangement. An optimized procedure for the thermal rearrangement ofaziridine 17 involved its heating in a dilute [10 mM] solution in1,4-dioxane at 180° C., in the presence of Cs₂CO₃, to provide thedesired dihydro[3]benzazepine 23 in low yield (30%). Variation in thearomatic substituents within the aziridine substrates was found to havea significant effect on the efficiency of the rearrangement. Forexample, the p-methoxyacetophenone-derived aziridine 18 was subjected tothe same thermal rearrangement conditions, resulting in itstransformation to the dihydro[3]benzazepine 24 with significantlyincreased efficiency (52%) compared to that of its predecessor 17→23.Likewise, rearrangement of aziridine 19, incorporating the3,4-methylenedioxy-substituted aryl group, resulted in the formation ofdihydro[3]benzazepine 25 in the most efficient example of therearrangement thus far (68%). As expected, the rearrangement proceededwith complete regioselectivity. (W. T. Dixon, Tetrahedron Lett. 1968,189; V. K. Dauksas, G. V. Purvaneckas, E. B. Udrenaite, V. L. Gineityteand A. V. Barauskaite, Heterocycles 1981, 15, 1395-1404) Rationales forthe favorable effect of electronically activating groups on the aromaticring in the rearrangement (i.e., 18/19→24/25) may arise from compressionof the HOMO-LUMO gap in a concerted [3,3]-sigmatropic rearrangement.Conversely, a stepwise ionic mechanism for rearrangement might also beenhanced by initial aziridine opening to form a stabilized benzyliccation (vide infra).

Although the rearrangements of aziridines 17-19 all provided thecorresponding dihydro[3]benzazepine products, one exception to thistrend was uncovered with the N-vinyl-2-arylaziridine substrate 26(Scheme 2-1), derived from the conjugate addition of aziridine 15 intoDMAD (57%). This substrate exhibited a clear propensity for a stepwiserearrangement pathway, as heating led exclusively to the formation ofthe pyrrole 27. Its formation can be rationalized by initial aziridineopening in 26 to form the highly reactive p-quininone methide zwitterion28, presumably due to the enhanced electron-deficient character of itsN-vinyl substituent. Subsequent 5-exo cyclization by the C-nucleophileonto the benzylic position provided the dihydropyrrole 29, whichunderwent facile air oxidation to provide the substituted pyrrole 27.

Despite this final example of pyrrole formation (27, Scheme 2-1), themajority of examples of successful dihydro[3]benzazepine formation(23-25, Scheme 1-1) boded well for the synthesis of cephalotaxine (1).However, access to the tricyclic dihydro[3]benzazepine 25 wascompromised by the low yielding condensation of aziridine 15 withβ-chloroenone 16, reflecting a trend in which π-donor substituents onthe aromatic ring elicit a detrimental effect on theaddition-elimination step. Further investigation of this transformationrevealed that the N-vinylaziridine adduct 19 has an increasedsusceptibility to nucleophilic attack at its benzylic position,resulting in post-coupling chloride-mediated aziridine cleavage. Thus, aminor variation in the protocol to prepare dihydro[3]benzazepine 25 wasimplemented (Scheme 3-1). The addition of aziridine 15 into chloroenone16 was conducted at elevated temperature, resulting in the isolation ofbenzylic chloride 30 (64%). Treatment of β-chloroamine 30 with Cs₂CO₃ inTHF led to the generation of the desired dihydro[3]benzazepine 25 (68%),presumably via re-formation of the aziridine functionality in situ andsubsequent rearrangement. This sequence provided a means for large scaleaccess to dihydro[3]benzazepine 25, facilitating investigation into thechallenge of pyrrolidine construction.

Pyrrolidine Construction Via Azomethine Ylide 1,3-Dipolar Cycloaddition.The azomethine ylide 1,3-dipolar cycloaddition is a powerful tool forthe synthesis of highly substituted pyrrolidine rings within manycomplex alkaloid targets. (E. Vedejs and F. G. West, Chem. Rev. 1986,86, 941-955; K. V. Gothelf and K. A. Jorgensen, Chem. Rev. 1998, 98,863-909; C. Najera and J. M. Sansano, Curr. Org. Chem. 2003, 7,1105-1150; W. H. Pearson and P. Stoy, Synlett 2003, 903-921; I. Coldhamand R. Hufton, Chem. Rev. 2005, 105, 2765-2809) Many methods exist forthe generation of these transient 4π-electron dipoles, both instabilized and non-stabilized forms, wherein a common approach to theformation of the latter involves the desilylation of iminium saltintermediates. This strategy, first developed by Vedejs, (Vedejs, 1986,supra; E. Vedejs and G. R. Martinez, J. Am. Chem. Soc. 1979, 101,6452-6454) has seen use in a variety of complex molecule syntheses andhas spawned a number of variants. In particular, a method of Padwainvolves N-alkylation of vinylogous imidates with trimethylsilylmethylelectrophiles followed by desilylation. (A. Padwa, G. Haffmanns and M.Tomas, Tetrahedron Lett. 1983, 24, 4303-4306) Recently, we disclosed acomplementary strategy to generate non-stabilized azomethine ylides fromN—CH₂TMS substituted tertiary vinylogous amides via initial O-activationfollowed by desilylation. (M. T. Epperson and D. Y. Gin, Angew. Chem.Int. Ed. 2002, 41, 1778)

This method was found to be suitable for the generation of pyrrolidinestructures bearing a fully substituted carbon at the α-position, astructure that directly maps onto the C5-spiro-fused pyrrolidinesubstructure within cephalotaxine (1). These efforts commenced withN-alkylation of dihydro[3]benzazepine 25 (Scheme 4-1), accomplished withTMSCH₂I to afford the tertiary vinylogous amide 31 (62%). CarbonylO-activation of vinylogous amide 31 was performed by treatment withTf₂O. This was followed by the sequential addition of DMAD as anactivated dipolarophile and tetrabutylammoniumtriphenylsilyldifluorosilicate (TBAT) (A. S. Pilcher, H. L. Ammon and P.Deshong, J. Am. Chem. Soc. 1995, 117, 5166-5167) as the desilylatingagent. The cycloadduct 33, incorporating the C5-spiro-fused pyrrolidinecore of cephalotaxine, was isolated in 53% yield, indicating successfulgeneration and cycloaddition of the azomethine ylide 32.

Azomethine Ylide Generation from Vinylogous Amides Via SequentialO-Sulfonylation and Nucleophilic Exchange. The successful synthesis ofpyrrolidine 33 provided rapid access to the complete pentacyclic core ofcephalotaxine. Moreover, a vinyl triflate moiety was installed at C3,the position of acyl chain attachment in the cephalotaxus esters. Whilea number of avenues could have been pursued to use this functionality asa direct precursor for installation of the acyl side chain, thereexisted the possibility of adapting this key cycloaddition step not onlyto pyrrolidine formation, but also for concomitant installation of theacyl chain.

Implicit in this vinylogous amide activation protocol is the initialformation of the C3-vinylogous iminium triflate 34 (Scheme 5-1).Vinylogous iminium triflates have been demonstrated to engage inelectrophilic aromatic substitution reactions at the enol triflatecarbon center. (I. L. Baraznenok, V. G. Nenajdenko and E. S. Balenkova,Tetrahedron 1998, 54, 119-128; I. L. Baraznenok, V. G. Nenajdenko and E.S. Balenkova, Eur. J. Org. Chem. 1999, 937-941) That intermediates suchas 34 are susceptible to nucleophilic attack suggested the possibilityof its interception with an external nucleophile (Nu) prior toazomethine ylide formation and cycloaddition (34→35→36→38). Thispresented the prospect of directly introducing the cephalotaxus esterside chain in the pyrrolidine-forming event. Additionally, this pursuitmay find general utility in the preparation of differentiallyfunctionalized pyrrolidines from vinylogous amide precursors.

TABLE 1-1 Azomethine ylide generation from vinylogous amides viasequential O- sulfonylation and nucleophilic exchange.

Entry Nu^(⊖) Cycloadduct Yield (%) 1 Bu₄NI 40 (Nu = I) 52 2 Bu₄NBr 41(Nu = Br) 45 3 Bu₄NCl 42 (Nu = Cl) 52

The hypothesis was evaluated with a simple model vinylogous amide 39(Table 1-1), which was activated with Tf₂O. Subsequent introduction ofan activated dipolarophile (DMAD), a variety of halide nucleophiles, andTBAT, led to rapid cycloaddition at 23° C. Importantly, the externalhalide nucleophiles were successfully incorporated into the cycloadducts40-42 (entries 1-3), thereby validating the feasibility of this in situnucleophilic exchange protocol for azomethine ylide cycloadditions.

The concept was further extended to that of the cephalotaxus esters,involving exchange with external carboxylate nucleophiles. Activation ofthe dihydro[3]benzazepine-derived vinylogous amide 31 (Scheme 6-1A) withTf₂O was performed to provide the corresponding transienttriflyl-imidate. Prior to ylide formation via desilylation,triethylammonium benzoate was introduced to generate the correspondingacyl-imidate, which underwent subsequent azomethine ylide formation withTBAT and cycloaddition with DMAD to provide the C3-substitutedcycloadduct 43 in 35% yield. A significantly improved efficiency forthis reaction was achieved with cesium benzoate as the nucleophilicspecies, affording the cycloadduct 43 in 64% yield. While this promisingresult presented a convenient method for transient nucleophilic exchangein an azomethine ylide cycloaddition, the ultimate purpose for which itwas developed, that of introduction of an intact cephalotaxus ester sidechain in the cycloaddition event, met with no success. For example, theracemic cesium carboxylate 44 (Scheme 6-1B) was prepared from itaconicacid via a modification of the sequence of Weinreb (J. Auerbach, T.Ipaktchi and S. M. Weinreb, Tetrahedron Lett. 1973, 4561-4564), and wasintroduced as a nucleophilic exchange reagent for the azomethine ylidecycloaddition with vinylogous amide precursor 31. Unfortunately, none ofthe desired cycloadduct 45, incorporating the deoxyharringtonine acylchain, was detected in this operation, despite extensive attempts atoptimization.

Asymmetric Synthesis of (−)-Cephalotaxine (I). Azomethine YlideGeneration and Cycloaddition Via O-Acylation of Vinylogous Amides. Whilethe aziridine-rearrangement/dipolar-cycloaddition reactions (Schemes 5-1and 10-1) remained at the heart of the synthetic plan, the goal ofinstalling the acyl chain in an operation concomitant with azomethineylide cycloaddition was set aside in favor of pursuing an asymmetricconstruction of the cephalotaxine core 1 as the initial target.Investigations on this front were initiated to determine theresponsiveness of the 1,3-dipolar cycloaddition reaction to elements ofrelative stereochemical control in the formation of the C5-spiro ringfusion. Thus, a chiral azomethine ylide such as 46 (Scheme 7-1),incorporating proximal C1 and C2 substituents, was anticipated to biasfacial-selective approach of the dipolarophile. (Exhaustiveinvestigation of azomethine ylide precursors incorporating only a C2group led to no diastereoselectivity in the cycloaddition.) Such asubstrate was envisioned to take the form of β-chloroenone 53 (Scheme8-1), which could be prepared in non-racemic form from D-ribose.

The early incarnation of the synthesis of chloro-enone 53 relied on akey olefination sequence first reported by Borchardt and coworkers, (S.M. Ali, K. Ramesh and R. T. Borchardt, Tetrahedron Lett. 1990, 31,1509-1512; A. Blaser and J. L. Reymond, Helv. Chim. Acta 1999, 82,760-768; C. K. Chu, Y. H. Jin, R. O. Baker and J. Huggins, Bioorg. Med.Chem. Lett. 2003, 13, 9-12) and indeed provided initial quantities ofβ-chloroenone 53 for investigation. (Eckelbarger, supra) However, wefound the above-mentioned olefination reaction to be unreliable inefforts to secure larger workable quantities of this intermediate. As aresult, a second generation synthesis of 53 was developed (Scheme 8-1).The selectively protected D-ribofuranose 48 (J. S. Yadav, S. Pamu, D. C.Bhunia and S. Pabbaraja, Synlett 2007, 992-994) was treated withtriphenylphosphonium methylide to effect C1 olefination (75%). This wasfollowed by C4 oxidation (SO₃.Pyr) to afford enone 49 (88%). Addition ofvinyl magnesium bromine to ketone 49 proceeded stereo selectively (8:1dr) via Cram chelation control to provide the allylic alcohol 50 (93%),whose 1,6-diene functionality underwent ring closing olefin metathesis(Grubbs-II) to afford the cyclopentene 51 (95%). (Y. H. Jin, P. Liu, J.N. Wang, R. Baker, J. Huggins and C. K. Chu, J. Org. Chem. 2003, 68,9012-9018) Regioselective chloroselenylation of the alkene within 51followed by selenide oxidation and elimination afforded thechlorocyclopentene 52 (98%). Finally, silyl ether deprotection revealeda vicinal diol (99%), which underwent periodate-mediated oxidativecleavage to furnish the chiral β-chloroenone 53 (90%) in a robust andscalable synthetic sequence.

Use of β-chloroenone 53 in the synthesis of the dihydro[3]benzazepinecore of cephalotaxine (1) involved addition-elimination with the racemicaziridine nucleophile 15 at ambient temperature (Scheme 9-1). Thisafforded a 1:1 diastereomeric mixture of the N-vinyl aziridine 54 (85%),interestingly with no evidence of chloride induced aziridine opening(cf. 30, Scheme 3-1). Heating of a dilute solution of 54 in 1,4-dioxaneled to efficient rearrangement to afford the dihydro[3]benzazepine 55(76%).

It is worth noting that although the rearrangement precursor 54 existedas a 1:1 mixture of diastereomers, the formation of 55 proceeded in >50%yield. This implies that the C11-R diastereomer 54a (Scheme 10-1) likelyproceeded through an aziridine rupture step prior to azepine formation.For example, if the rearrangement occurred in a concerted fashion, astrain-release variant involving an internal aziridine ring wouldnecessitate an endo-disposed boat-like transition state (Scheme 10-1),such as 56a for the C11-R-diastereomer 54a, or 56b for theC11-S-diastereomer 54b. While the concerted conversion of theC11-S-diastereomer 54b to 57 via the transition state 56b appearsreasonable, direct rearrangement of the C11-R-diastereomer 54a isunlikely, given the severe steric interaction between the aryl ring andthe isopropylidene ketal in transition state 56a. As a consequence, theC11-R-diastereomer 54a could relieve this strain by first forming thep-quinone methide zwitterion 58 followed by re-closure to theC11-S-diastereomer 54b prior to sigmatropic rearrangement via 56b.Conversely, if a stepwise ionic mechanism is invoked, both aziridinediastereomers may open to the common p-quinone methide zwitterion 58,followed by 7-exo-trig cyclization to afford the azepine 57.

At this stage, advancement of the pentacyclic dihydro[3]benzazepine 55to cephalotaxine (1) relied on the 1,2-di-O-isopropylidene substituentto serve as a chiral controller in establishing the stereoselectivity ofthe key azomethine ylide cycloaddition. The dihydro[3]benzazepine 55(Scheme 11-1) was N-alkylated with TMSCH₂I to afford the tertiaryvinylogous amide 59. O-Activation of the vinylogous amide group in 59was then investigated with an electrophilic agent distinct from Tf₂O inorder to preclude any possibility of nucleophilic exchange involving thetransient iminium intermediate (vide supra). As a result, the highlyreactive acyl electrophile, pivaloyl triflate, generated in situ by thereagent combination of pivaloyl chloride and AgOTf, (F. Effenberger, J.K. Eberhard and A. H. Maier, J. Am. Chem. Soc. 1996, 118, 12572-12579)proved suitable for this purpose. Subsequent desilylation with TBAT ledto azomethine ylide formation (60) and cycloaddition with phenyl vinylsulfone, affording the spiro-fused pyrrolidine 62 (77%) as a singleconstitutional stereoisomer. This high level of stereoselectivity in thecycloaddition signals the effectiveness of the C1-C2 isopropylideneketal as a stereodetermining element, albeit with an unanticipatedresult.

With the formation of the putative non-stabilized azomethine ylide 60,the phenylvinyl sulfone dipolarophile was initially thought to approachthe dipole face distal to the isopropylidene ketal (i.e., 63) in anearly transition state. This would lead to the generation of a C5-Scycloadduct 64, which would be appropriate for the synthesis of ent-(1)as an enantiomeric model system. However, the sole product ofcycloaddition, 62, possessed the C5-R configuration, verified by singlecrystal X-ray analysis. While this unexpected outcome provided aconvenient means to access the natural enantiomer of cephalotaxine fromnaturally abundant D-ribose, the reason for the stereochemical outcomeis unclear. Favorable bias for transition state 61 over 63 could berationalized in a late transition state model where the nitrogen atom issignificantly pyramidalized. (D. H. Ess and K. N. Houk, J. Am. Chem.Soc. 2007, 129, 10646) As a consequence, transition structure 61, withα-approach of the dipolarophile, would lead to a smaller net dipolegiven that the developing nitrogen lone pair is oriented opposite tothat of the electronegative oxygen atoms of the isopropylidene ketal. Bycontrast, β-approach of the dipolarophile (63) would lead to anenhancement of a net dipole, despite a more sterically forgivingarrangement of atoms. This dipole moment rationalization, be it in aconcerted cycloaddition or a stepwise ionic mechanism, is of coursepredicated on a kinetically controlled reaction. Indeed, one cannotdiscount the possibility of thermodynamic selection via either areversible cycloaddition process, or post-cycloaddition C5-epimerizationpathways such as reversible trans-annular ring fragmentation.Unfortunately, these hypotheses could not be explored since the C5-Sdiastereomer 64 could not be detected.

The remaining sequence in the non-racemic synthesis of (−)-cephalotaxine(1) involved functional group manipulations of hexacyclic cycloadduct 62(Scheme 12-1). Reductive desulfurization of 62 to produce pyrrolidine 65(74%) proceeded with SmI₂ in the presence of HMPA (H. Kunzer, M.Stahnke, G. Sauer and R. Wiechert, Tetrahedron Lett. 1991, 32,1949-1952; D. Craig, P. S. Jones and G. J. Rowlands, Synlett 1997,1423-1425) with 10 equiv of t-BuOH as a proton source to avoid ruptureof the pyrrolidine ring via elimination. Subsequent experimentationrevealed that the pivaloate enol ester moiety in 65 was recalcitrant toboth hydrolysis and hydrogenation. As a result, reductive cleavage ofthe enol ester in 65 was performed with Schwartz' reagent (J. Schwartzand J. A. Labinger, Angew. Chem. Int. Ed. 1976, 15, 333-340; N. Cenac,M. Zablocka, A. Igau, J. P. Majoral and A. Skowronska, J. Org. Chem.1996, 61, 796-798) to provide the enol 66 (99%), which was thenre-acylated with benzyl chloroformate and KHMDS to provide the enolbenzyl carbonate 67 (86%). Interestingly, when Et₃N was used as base forthis transformation, N-acylation occurred with concomitant β-eliminationto afford enone 68. Differentiation of the C1 and C2 oxygen substituentsin 67 was then initiated with isopropylidene removal (99%).Regioselective derivatization of the corresponding diol provedchallenging, as several attempts at regioselective silylation,acylation, and alkylation with numerous reagent combinations wereunsuccessful. The only suitable derivatization protocol involved theLewis acid catalyzed acylation procedure of Clarke and co-workers, (P.A. Clarke, R. A. Holton and N. E. Kayaleh, Tetrahedron Lett. 2000, 41,2687-2690; P. A. Clarke, N. E. Kayaleh, M. A. Smith, J. R. Baker, S. J.Bird and C. Chan, J. Org. Chem. 2002, 67, 5226-5231; P. A. Clarke, P. L.Arnold, M. A. Smith, L. S, Natrajan, C. Wilson and C. Chan, Chem.Commun. 2003, 2588-2589) in which treatment of the C1,C2-diol with Boc₂Oand Yb(OTf)₃, necessarily in its polyhydrated form, led to selectiveC1-O-acylation. Subsequent C2-oxidation using IBX furnished enone 69(50%, from 67), allowing for CrCl₂-mediated reductive deoxygenation ofthe Boc carbonate and benzylcarbonate hydrogenolysis to provide the enol70 (42%, 2 steps). Sequential methyl enol ether derivatization of the C2ketone and stereoselective reduction of the C3 enol functionality withNaBH₄ (Isono, supra) concluded the synthesis of (−)-cephalotaxine (1)(Eckelbarger, supra).

Synthesis and Attachment of the Acyl Chain of Antitumor CephalotaxusEsters. The bulk of the synthetic reports concerning the cephalotaxusalkaloids have focused on cephalotaxine (1). On the other hand, reportson the synthesis of natural anti-leukemia cephalotaxus esters have beenrelatively scarce, likely a result of the difficulties associated withappending a fully intact acyl side chain onto the C3-OH ofcephalotaxine. The challenge of such an acylation arises from extensivesteric obstruction, marked by the secondary C3-hydroxyl nucleophileburied within the concave face of cephalotaxine, and exacerbated by afully α-substituted acyl electrophile in the side chain. Indeed, thedifficulty of this acylation event is highlighted in numeroussemi-syntheses of the cephalotaxus esters from cephalotaxine (1, seeChart 1), wherein the bulk of these efforts employed a less hinderedprochiral C2′-sp² hybridized side chain derivative in the acylationevent, followed by subsequent non-stereoselective functional groupmanipulation. (K. L. Mikolajczak, C. R. Smith, Weislede. D, T. R. Kelly,J. C. McKenna and Christen. Pa, Tetrahedron Lett. 1974, 283-286; K. L.Mikolajczak and C. R. Smith, J. Org. Chem. 1978, 43, 4762-4765; S.Hiranuma and T. Hudlicky, Tetrahedron Lett. 1982, 23, 3431-3434; S.Hiranuma, M. Shibata and T. Hudlicky, J. Org. Chem. 1983, 48, 5321-5326)A notable exception to this strategy used an acyl chain substratespecifically appropriate for homoharringtonine in which the C1″-estermoiety was constrained as a cyclic derivative to allow for acylationwith the C1′-electrophile. (T. R. Kelly, R. W. McNutt, M. Montury, N. P.Tosches, K. L. Mikolajczak, C. R. Smith and D. Weisleder, J. Org. Chem.1979, 44, 63-67) This approach was introduced with racemic substratesand has recently evolved to non-racemic examples whereinenantio-enriched side chain substrates were prepared in >10-stepsequences. (J. P. Robin, R. Dhal, G. Dujardin, L. Girodier, L. Mevellecand S. Poutot, Tetrahedron Lett. 1999, 40, 2931-2934)

Since the most pressing late-stage challenge in the synthesis of thecephalotaxus esters is the efficient attachment of hindered acyl chainderivatives, an approach was explored whereby novel bond angle strainelements were imparted to these substrates to enable their use in highyielding acylations of cephalotaxine (1). This strategy initially led tothe facile synthesis deoxyharringtonine (2), and subsequently to othermembers of this alkaloid class, namely anyhydroharringtonine (5),homoharringtonine (3), and homodeoxyharringtonine (4) (i.e., see FIG.1).

The initial steps in the synthesis of several cephalotaxus acyl chainsinvolved the application of the Seebach concept of “self-reproduction ofchirality,” (D. Seebach, R. Naef and G. Calderari, Tetrahedron 1984, 40,1313-1324) an approach that has shown promise in the preparation ofchiral non-racemic α-alkylmalates. (S. A. A. El Bialy, H. Braun and L.F. Tietze, Eur. J. Org. Chem. 2005, 2965-2972; P. Q. Huang and Z. Y. Li,Tetrahedron: Asymmetry 2005, 16, 3367-3370) Beginning with R-malic acid(71, Scheme 13-1) as a readily available chiral starting material, itsC1′ carboxylic acid and C2′ hydroxyl were tethered by a t-butyl acetalupon treatment with pivaldehyde and TMSOTf. Only a single diastereomerof the acetal 72 was observed (82%), after which double deprotonationwas induced with excess LHMDS. Although the formation of dilithiumcarboxylate-enolate 73 resulted in destruction of the CT stereocenter,its stereochemical information was preserved in the chiral acetal carbonbearing the t-butyl group. This sterically demanding substituent forcedenolate alkylation with prenyl bromide from the distal face, therebysecuring the C2′-R configuration in 74 (66%). Transesterification of 74with NaOBn removed the acetal to afford benzyl ester 75 (88%) as asingle enantiomer.

In an effort to facilitate the esterification of cephalotaxine (1), thestrategy of constraining both the C2′-hydroxyl and the C1″-carboxylicacid in 75 into a β-lactone functionality such as 76 appearedattractive. The strain energy arising from endocyclic bond anglecompression within β-lactone ring in 76 would necessarily induceexocyclic bond angle expansion, thereby relieving local stericcongestion at the electrophilic C1′ site. Moreover, the angle strain ina four-membered ring imparts higher hybrid orbital s-character in theexocyclic bonds, an effect that could result in increased Celectrophilicity through induction. In addition, the increasedp-character of the endocyclic bonds within the β-lactone may also aid instabilizing the formation of C1′-acylium like intermediates in activatedester derivatives of 76 through vicinal π-delocalization. Despite thesepotential advantages, however, the strain associated with the β-lactonemoiety in 76 could also serve to be a liability, as undesired ringexpansion reaction manifolds may ensue upon C1′-ester activation.

Nevertheless, these aspects were investigated by the treatment ofhydroxy acid 75 with 2,4,6-Cl₃C₆H₂COCl (J. Inanaga, K. Hirata, H. Saeki,T. Katsuki and M. Yamaguchi, Bull. Chem. Soc. Jpn. 1979, 52, 1989-1993)to afford the corresponding β-lactone, which was subsequently treatedwith H₂ and Pd to reduce both the alkene and the benzyl ester to affordthe carboxylic acid 76 (50%, 2 steps). Fortunately, activation of theacid 76 as the Yamaguchi mixed anhydride allowed for efficient acylationof cephalotaxine to form the ester I-3a (81%, 23° C., <1 min) withoutcompromising the integrity of the β-lactone. Subsequent methanolysis ofthe β-lactone provided (−)-deoxyharringtonine (2, 76%), whose spectraldata was identical to that of the natural product. To get a bettermeasure of the beneficial effects of the β-lactone moiety in theacylation step, an analogous acyclic acyl electrophile 78 was prepared,beginning with trimethylsilyldiazomethane treatment of hydroxy acid 75to afford the methyl ester 77 (>99%). Acetylation of the C2′ hydroxylgroup in 77 followed by benzyl ester hydrogenolysis and alkenehydrogenation provided the carboxylic acid 78 (74%, 2 steps), which wasdevoid of the ring strain elements present in the β-lactone 76. Attemptsat cephalotaxine acylation with 78 under otherwise identical conditionsled to only trace quantities of protected deoxyharringtonine.Furthermore, heating of the reaction for several hours was alsounsuccessful, signaling the critical beneficial effect of the β-lactonemoiety in 76 in the synthesis of the bioactive cephalotaxus esters.

The successful synthesis of deoxyharringtonine (2) also allowed forrapid access to the anti-leukemia alkaloid anhydroharringtonine (5)through interception of the chiral hydroxy diester 77 (Scheme 14-1),previously prepared in the acylation studies toward 2 (see Scheme 13-1).This substrate was subjected to intramolecular alkene alkoxymercurationand reduction (Scheme 14-1) to furnish the corresponding tetrahydrofuran(77%). Subsequent benzyl ester hydrogenolysis provided the acylationprecursor 80 (99%). Although the strain imparted by the tetrahydrofuranring in 80 is significantly less than that of β-lactone 76 in thesynthesis of 2, the use of 80 in the acylation of cephalotaxine produced(−)-anhydroharringtonine (5) in excellent yield (99%, 23° C., 1 hr), yetwith a significantly extended reaction time (i.e., 1 hr for 80 asopposed to <1 min for 76). This effort furnished two natural productcephalotaxus esters (2 and 5), as well as a host of non-naturalsynthetic intermediates for expansive antitumor evaluation.

Anti-Proliferative Activity of Deoxyharringtonine (2), β-Lactone I-3a,and Anhydroharringtonine (5). The completion of the synthesis ofdeoxyharringtonine (2) and anhydroharringtonine (5) permitted, for thefirst time, an expanded evaluation of their in vitro cytotoxicity.Following the early screening of the cephalotaxus esters against murineP388 and L1210 cell lines, (R. G. Powell, Weislede. D and C. R. Smith,J. Pharm. Sci. 1972, 61, 1227) many of the cytotoxic evaluations focusedon leukemia and lymphoma, with comparatively fewer reports on activityprofiles against solid tumor cell lines. (Kantarjian, supra) As aresult, deoxyharringtonine (2), anhydroharringtonine (5), and theβ-lactone intermediate I-3a (generated in the synthesis of 2, Scheme13-1) were evaluated against a variety of human hematopoietic and solidtumor cell lines (Table 2). (C. Antczak, D. Shum, S. Escobar, B. Bassit,E. Kim, V. E. Seshan, N. Wu, G. L. Yang, O. Ouerfelli, Y. M. Li, D. A.Scheinberg and H. Djaballah, J. Biomol. Screening 2007, 12, 521-535; D.Shum, C. Radu, E. Kim, M. Cajuste, Y. Shao, V. E. Seshan and H.Djaballah, Journal of Enzyme Inhibition and Medicinal Chemistry (inpress)) These include HL-60 (acute promyelocytic leukemia), HL-60/RV+ (aP-glycoprotein over-expressing multidrug resistant HL-60 variant whichwas selected by continuous exposure to the vinca alkaloid vincristine),JURKAT (T cell leukemia), ALL3 (acute lymphoblastic leukemia recentlyisolated from a patient treated at MSKCC and characterized asPhiladelphia chromosome positive), NCEB1 (Mantle cell lymphoma), JEKO (Bcell lymphoma), MOLT-3 (acute lymphoblastic T-cell), SKNLP(neuroblastoma), Y79 (retinoblastoma), PC9 (adenocarcinoma), H1650(adenocarcinoma), H1975 (adenocarcinoma), H2030 (adenocarcinoma), H3255(adenocarcinoma), TC71 (Ewing's sarcoma), HTB-15 (glioblastoma), A431(epithelial carcinoma), HeLa (cervical adenocarcinoma), and WD0082(well-differentiated liposarcoma).

Several general features are evident in the cytoxicity data accumulatedin the initial screening campaigns (Table 2). As expected, evaluation ofdeoxyharringtonine (2) revealed exceedingly potent cytotoxic activityagainst all of the hematopoietic cell lines tested (HL-60, HL-60/RV+,JURKAT, ALL3, NCEB1, JEKO, MOLT-3); moreover, the alkaloid exhibitedsimilarly high activity against most of the solid tumor cell linestested (SKNLP, PC9, H1650, H1975, H2030, H3255, A431, HeLa, TC71,HTB-15, WD0082). Interestingly, the late-stage β-lactone variant I-3a(see also Scheme 13-1) exhibited significant cytotoxicity, yet atattenuated levels compared to the parent alkaloid 2, revealing thelikely necessity of a hydroxyl group or an H-bond donor functionality atthe C2′-position. Surprisingly, the cytoxicity profile ofanhydroharringtonine (5) revealed fairly poor antitumor activity. Whilean early report noted comparable cytotoxic activity ofanhydroharringtonine (5) to that of deoxyharringtonine (2) againstmurine P388, (Wang, 1992, supra) the present result indicates that theactivity of 5 is generally several orders of magnitude lower in humanHL-60 tumor cells. This unimpressive potency level of 5 thus effectivelydisqualifies it as a potential therapeutic agent despite previouscytotoxicity data, and is consistent with the proposed need for a2′-hydroxy group in the acyl chain to confer adequate activity (videsupra).

Synthesis of Additional Cephalotaxus Ester Natural Products and Variantsto Probe Susceptibility to Multidrug Resistant Cancer. The developmentof vincristine-resistance in cancer cells, such as HL-60/RV+ (Table 2)is believed to arise from classic multidrug resistance (MDR). Thisinvolves the overexpression of ATP-dependent efflux pumps, such asP-glycoprotein (Pgp) and multidrug resistance-associated protein (MRP),leading to expulsion of natural product hydrophobic drugs (e.g., vincaalkaloids, anthracyclines, actinomycin-D, paclitaxel) from thetransformed cell. (M. M. Gottesman, T. Fojo and S. E. Bates, Nat. Rev.Cancer 2002, 2, 48-58) Previous reports have noted that the activity ofhomoharringtonine (3), the cephalotaxus ester currently being evaluatedin clinical trials, is also compromised in MDR human leukemia cells.(Benderra, supra) Remarkably, the susceptibility of MDR cancer cells todifferent cephalotaxus esters has not been systematically probed.Prevention of MDR would significantly improve therapeutic response tothis family of chemotherapeutics and extend their use in the clinic. Onepossible way to achieve this would be to develop anticancer agents thatare not substrates for these ATP-dependent transporters, thus overcomingtheir efflux from cells.

In examining variations in potencies of deoxyharringtonine (2) againstthis extensive panel of cell lines (Table 2), it is worth noting thatits activity against vincristine-resistant HL-60/RV+ cells (IC₅₀ 0.22μM), relative to its non-resistant counterpart HL-60 (IC₅₀ 0.02 μM),shows only a ˜10-fold decrease in potency. This trend is also reflectedin the β-lactone derivative I-3a (albeit with lower absolutecytotoxicity levels). This rather low observed 10-fold resistance indexspawned an interest in probing potential molecular design criteria thatmay offset MDR susceptibility in this class of alkaloids. Fortunately,our current synthetic approach to deoxyharringtonine (2) permits therapid and versatile attachment of sterically demanding acyl chains ontothe cephalotaxine core. Thus, the synthetic strategy todeoxyharringtonine (2) was further extended to the construction of twoadditional anti-leukemia cephalotaxus ester natural products, namelyhomoharringtonine (3) and homodeoxyharringtonine (4), all reported to bepotent antileukemia alkaloids.

The syntheses of homoharringtonine 3 and homodeoxyharringtonine 4involved a common early sequence (Scheme 15-1) beginning with theR-malic acid derived acetal 72, which underwent double deprotonation anddiastereoselective enolate alkylation with allyl bromide (59%).(Seebach, supra) Following NaOBn-mediated transesterification of theresultant acetal-ester to afford the R-α-hydroxy benzyl ester 81 (85%),β-lactone formation was accomplished via the Yamaguchi mixed anhydrideto provide the strained intermediate 82 (67%). Subsequent alkene crossmetathesis (Grubbs-II) with excess alkene 83 (R. G. Salomon and J. M.Reuter, J. Am. Chem. Soc. 1977, 99, 4372-4379; A. K. Chatterjee, T. L.Choi, D. P. Sanders and R. H. Grubbs, J. Am. Chem. Soc. 2003, 125,11360-11370) provided disubstituted alkene 85 (61%) along with thedimeric bis(lactone) 84 (22%) as an equilibrium mixture. Although thedirect conversion of 82 to 85 was moderate, the recovered dimer 84 couldbe re-equilibrated under olefin metathesis conditions with excess 83 toaccumulate additional quantities of 85. Following selective transferhydrosilylation of 85, the resultant acid 86 (85%) was employed in ahighly efficient cephalotaxine acylation to prepare the correspondingester (97%), whose β-lactone was then subjected to methanolysis tofurnish I-5 (79%). This intermediate was then diverged to both of thenatural products homoharringtonine (3) and deoxyhomoharringtonine (4).When the allylic benzyl ether in I-5 was subjected to Pd/C-catalyzedhydrogenolysis/hydrogenation in MeOH, followed by the addition of AcOHin the latter stages of the reaction, (−)-homoharringtonine (3, 79%) wasisolated (presumably through initial alkene hydrogenation followed bybenzyl ether hydrogenolysis). On the other hand, when the Pd/C-catalyzedreduction was performed in glacial AcOH solvent at the outset,deoxygenation preceded alkene reduction (presumably through E1elimination of the allylic benzyl ether prior to hydrogenation) toafford (−)-homodeoxyharringtonine (4, 69%).

The efficient synthesis of the acyl chain precursors in the preparationof the natural product cephalotaxus esters 3 and 4 also presented theopportunity to prepare a non-natural analogue for biological evaluationwith only a minor variation in the synthetic sequence. This analoguetook the form of bis(demethyl)deoxyharringtonine I-4 (Scheme 16-1), alsoanticipated to exhibit potent anti-proliferative activity, although muchsimpler in structure and more easily prepared than 3 or 4. The synthesisof cephalotaxus ester I-4 (Scheme 16-1) involved interception of theβ-lactone acyl chain 82, derived from R-malic acid in three steps (referto Scheme 15-1). Following hydrogenolysis/hydrogenation of the alkenylester 82 (97%), the resulting carboxylic acid was activated as theYamaguchi mixed anhydride to effect the acylation of cephalotaxine (1),providing the ester-β-lactone I-1 (81%). Methanolysis of the β-lactonein I-1 proceeded efficiently to afford the non-naturalbis(demethyl)deoxyharringtonine analogue I-4 (93%).

The completion of the syntheses of the natural cephalotaxus esters 2-4together with two non-natural synthetic analogues, namelybenzyldehydrohomoharringtonine I-5 and bis(demethyl)deoxyharringtonineI-4, permitted their comparative biological evaluation against“sensitive” and MDR tumor cell lines (FIG. 3). When tested against the“sensitive” HL-60 cell line, all were found to be exceedingly potent(IC₅₀<0.08 μM). When evaluated against the “resistant” HL60/RV+ cellline, stark differential response levels were observed within thiscollection of cephalotaxus esters (FIG. 4). Interestinglyhomoharringtonine (3) displayed a 125-fold decrease in activity towardHL-60/RV+ relative to that of HL-60 (resistance index=125). By contrast,much lower resistance indices of 11, 3, 12, and 19 were observed withthe esters 2, 4, I-5, and I-4, respectively, indicating that theselatter natural and non-natural products are significantly lesssusceptible to MDR. One possible explanation for the high MDRsusceptibility of homoharringtonine (3) is its decreased lipophilicityas a consequence of its acyl chain structure, thereby rendering it agood substrate for the efflux pumps.

The relationship of the calculated lipophilicity values (c-log P) to theresistance indices for the highly potent cephalotaxus esters 2-4, I-5,and I-4 is presented in FIG. 4, wherein compounds with c-log P valuesgreater than 1.2 lead to generally low susceptibility to MDR (i.e.,resistance indices ≦19 for the cephalotaxus esters 2, 4, I-5, and I-4).The exception is homoharringtonine (3), exhibiting a relatively lowc-log P value (0.95, relatively more polar) to reflect an increasedsusceptibility to MDR (i.e., resistance index 125). Although these datawere obtained on a limited set of analogs, they provide for the firsttime new insights into the contribution of acyl chain structuremodification toward overcoming MDR resistance for this class ofcompounds.

It is worth emphasizing that the only structural difference on the acylchain between homoharringtonine (3) and homodeoxyharringtonine (4) is ahydroxyl group on the 6′-position (FIG. 4). While only a minorstructural perturbation, this 6′-substitution difference drasticallyaffects the lipophilicity of the molecules, ranging from a c-log P valueof 0.95 (polar) for 3 to a more hydrophobic compound 4 with a c-log Pvalue of 2.33 (i.e., FIG. 5). Importantly, with a resistance index ofonly 3 (as in the case with homodeoxyharringtonine 4), both comparativecell lines can be considered as “sensitive” to the compound of interest.As a consequence, this minor structural variation from 3 to 4 hasallowed for effective quelling of MDR resistance in this cell line.Given this finding, it is thus surprising that despite its MDRliability, homoharringtonine (3) is employed as the favored cephalotaxusester for advancement in the clinic, exemplified by a current phase IIIclinic prospective trial with 3 for use as a combination therapy forchronic myeloid leukemia. (L. Legros, S. Hayette, F. E. Nicolini, S.Raynaud, K. Chabane, J. P. Magaud, J. P. Cassuto and M. Michallet,Leukemia 2007, 21, 2204-2206) One practical reason for this may lie inthe increased natural abundance of homoharringtonine (3) relative toother cephalotaxus esters. (R. G. Powell, Phytochemistry 1972, 11, 1467)Moreover, semisynthetic sources of homoharringtonine have built on theseminal work of Kelly, wherein the 6′-oxygen functionality is aprerequisite for efficient acyl chain attachment to cephalotaxine.(Kelly, 1989, supra) Notably, this semi-synthetic approach is uniquelysuited for homoharringtonine (3). Fortunately, the synthetic strategiesdescribed herein enable unfettered access to other, more therapeuticallyviable cephalotaxus esters, such as 2, 4, I-5, and I-4, for thedevelopment of additional lines of chemotherapeutic defense againstleukemia.

Resistance of Vincristine-Sensitive Y79 Retinoblastoma to CephalotaxusEsters. In the initial cytotoxicity evaluation (Table 2), it is alsoworth highlighting that the Y79 retinoblastoma cell line uniquely showedsignificant resistance to both deoxyharringtonine (2) and its β-lactonederivative I-3a. Indeed, this selective resistance of Y79 appears to bea general phenomenon (Table 3) upon evaluation with a few of our activecytotoxic non-natural synthetic cephalotaxus ester analogues, includingthe benzyldehydrohomoharringtonine I-5, the β-lactone ester I-1, andbis(demethyl)deoxyharringtonine I-4. All of these compounds behavedsimilarly to that of deoxyharringtonine (2) and its β-lactone derivativeI-3a (cf. Table 2), exhibiting broad spectrum cytoxicity with theexception of the Y79 cell line, to which the molecules were essentiallyimpotent.

Though this specific lack of cytotoxicity in Y79 could also beattributed to the overexpression of multidrug resistance genes (MDR),Conway and co-workers have reported the Y79 cell line to be sensitive tovincristine with an IC₅₀ value of approx 0.8 μM. (R. M. Conway, M. C.Madigan, F. A. Billson and P. L. Penfold, Eur. J. Cancer 1998, 34,1741-1748) Furthermore, a comparative microarray analysis of the Y79cell line with normal retinal tissue detected upregulation of severalgenes typically found to be markers of stem cell like characteristicsincluding the mdr gene ABCG2. (G. M. Seigel, A. S. Hackam, A. Ganguly,L. M. Mandell and F. Gonzalez-Fernandez, Mol. Vis. 2007, 13, 823-832)Based on this, we postulate that perhaps the mechanism of resistance tocephalotaxus esters by Y79 is not entirely mediated through theclassical ATP-dependent efflux pumps alone but rather through an as yetunknown mechanism involving stem cell like characteristics. This isconsistent with the hypothesis that the appearance of subsequent tumorsin leukemias, brain tumors, breast cancer, lung cancer, as well as manyother cancers, is linked to the persistence of cancer stem cells. Thisobservation suggests that designed cephalotaxus esters have thepotential to serve as small molecule probes for interrogating thegenetic basis of this highly resilient retinoblastoma cell line as wellas potentially shedding some light on how to overcome this persistencephenomena in these dormant progenitor cancer stem cells.

Conclusion

The development, optimization, and application of novel syntheticstrategies have enabled the synthesis of the potent anti-leukemia agents(−)-deoxyharringtonine (2), (−)-homoharringtonine (3),(−)-homodeoxyharringtonine (4), and (−)-anhydroharringtonine (5).Several advances served as key elements in the preparation of(−)-cephalotaxine (1) and should find general applicability in complexN-heterocycle synthesis. These included (1) a strain-release aziridinerearrangement of 2-aryl-N-vinyl aziridines for dihydro[3]benzazepinesynthesis, and (2) a vinylogous amide-derived azomethine ylidecycloaddition which takes an unusual and unexpected stereochemicalcourse. Efforts to advance these synthetic pursuits beyond that of (−)-1to that of the rare anti-neoplastic C3-O-ester derivatives (i.e., 2-5)have led to an efficient non-racemic synthesis of several cephalotaxusacyl chains. Construction of strained β-lactone intermediates enabledlate-stage C3-O-acylation of cephalotaxine, a long-standing challenge inthe synthesis of sterically congested bioactive cephalotaxus esters.This technology enabled cytotoxicity screening of several natural andnon-natural cephalotaxus esters against an expansive array of humanhematopoietic and solid tumor cell lines. These evaluations wereinstrumental in discovering novel non-natural cephalotaxus esters withpotent antitumor effects. Moreover, these efforts have uncovered thepotential of specific members of this family of alkaloids to overcomeresistance in MDR HL-60/RV+ tumor cells through the preparation of acylchain variants, uniquely made available with our acyl chain attachmentapproach. This presents new avenues for molecular design of thesealkaloids to offset multi-drug resistance, offering new lines ofchemotherapeutic defense against leukemia and other cancers.

Experimentals

General Procedure for the Preparation of Oximes 10, 11, 12:

1-Benzo[1,3]dioxol-5-yl-ethanone oxime (12). Powdered sodium hydroxide(6.6 g, 170 mmol, 9.0 equiv) and hydroxylamine hydrochloride (3.8 g, 55mmol, 3.0 equiv) were sequentially added to a stirred suspension of and3,4-(methylenedioxy)acetophenone (9) (3.0 g, 18 mmol, 1.0 equiv) inethanol (32 mL) and distilled water (13 mL) at 25° C. The reactionvessel was equipped with a reflux condenser and heated to 80° C. via oilbath for 3 h. The reaction mixture was cooled to 25° C., diluted withsaturated aqueous ammonium chloride (400 mL), and the product wasextracted with dichloromethane (5×125 mL). The combined organic layerswere dried (sodium sulfate), gravity filtered, and concentrated byrotary evaporation. The residue was purified by rinsing with colddichloromethane followed by vacuum filtration to afford 12 (2.9 g, 87%yield) as an off-white crystalline solid. R_(f)=0.41 (25% ethyl acetatein hexane); ¹H NMR (500 MHz, CDCl₃) δ 7.77 (s, 1H, OH), 7.18 (d, 1H,J=1.5 Hz, ArH), 7.10 (dd, 1H, J=6, 1.5 Hz, ArH), 6.81 (d, 1H, J=6 Hz,ArH), 5.99 (s, 2H, OCH₂O), 2.24 (s, 3H, CH₃); IR (neat film) 3296 (w,br), 3228 (w, br), 2907 (w), 1505 (s), 1266 (s), 1227 (s), 1037 (s)cm⁻¹; HRMS (EI) m/z: Calcd for C₉H₉NO₃ (M⁺) 179.0582, observed 179.0584.

General Procedure for the Preparation of Aziridines 13, 14, 15:

2-Benzo[1,3]dioxol-5-yl-aziridine (15). A solution of oxime 12 (2.7 g,15 mmol, 1.0 equiv) in tetrahydrofuran (60 mL) at 25° C. was transferredvia cannula to a stirred suspension of lithium aluminum hydride (3.5 g,61 mmol, 4.0 equiv) and di-iso-propyl amine (8.5 mL, 61 mmol, 4.0 equiv)in tetrahydrofuran (70 mL) at 25° C. The emptied reaction vessel wasrinsed with tetrahydrofuran (22 mL) and the resulting solution was alsotransferred via cannula. The reaction vessel was equipped with a refluxcondenser under nitrogen atmosphere and heated to 60° C. via oil bathfor 4 h. The mixture was cooled to 25° C., diluted with ice water (400mL), and the product was extracted with dichloromethane (5×200 mL). Thecombined organic layers were dried (sodium sulfate), gravity filtered,and concentrated by rotary evaporation. The residue was purified bysilica gel column chromatography (5% triethylamine in ethyl acetate) toafford 15 (2.17 g, 88% yield) as a pale yellow oil. R_(f)=0.40 (5%triethylamine in ethyl acetate); ¹H NMR (500 MHz, CDCl₃) δ 6.75 (br s,2H, ArH), 6.70 (br s, 1H, ArH), 5.93 (s, 2H, OCH₂O), 2.97 (br s, 1H,ArCH), 2.17 (br s, 1H, CH₂), 1.67 (br s, 1H, CH₂).

3-Chloro-cyclopent-2-enone (16). A solution of oxalyl chloride (0.17 mL,2.0 mmol, 2.0 equiv) in dichloromethane (2.5 mL) at 0° C. wastransferred via cannula to a stirred suspension of 1,3-cyclopentanedione(S1) (98 mg, 1.0 mmol, 1.0 equiv) in dichloromethane (2.5 mL) at 0° C.The resulting yellow solution was stirred at 0° C. for 2 h, allowed towarm to 25° C., and stirred for 1 h. The reaction mixture was dilutedwith ice water (100 mL) and the product was extracted withdichloromethane (4×75 mL). The combined organic layers were dried(sodium sulfate), gravity filtered, and concentrated by rotaryevaporation to afford 16 (115 mg, 99% yield) as a brown oil. R_(f)=0.75(25% hexane in ethyl acetate); ¹H NMR (500 MHz, CDCl₃) δ 6.23 (t, 1H,J=2 Hz, vinyl H), 2.88 (m, 2H, CH2), 2.57 (m, 2H, CH2); IR (neat film)3089 (w), 2927 (w), 1716 (s), 1592 (s), 1259 (m), 1229 (m), 1036 (m),824 (w) cm-1; HRMS (EI) m/z: Calcd for C₅H₅OCl (MH⁺) 116.0029, observed116.0029.

3-(2-phenyl-aziridin-1-yl)-cyclopent-2-enone (17). A solution ofchloroenone 16 (140 mg, 1.2 mmol, 1.1 equiv) in tetrahydrofuran (3.5 mL)at 25° C. was transferred via cannula to a stirred solution of aziridine13 (130 mg, 1.1 mmol, 1.0 equiv) and triethylamine (0.19 mL, 1.4 mmol,1.2 equiv) in tetrahydrofuran (4.0 mL) at 25° C. The reaction vessel wassealed under argon and heated to 60° C. via oil bath for 24 h. Thereaction mixture was cooled to 25° C. and concentrated by rotaryevaporation. The residue was purified by silica gel columnchromatography (5% triethylamine in ethyl acetate) to afford 17 (130 mg,58% yield) as a brown oil. R_(f)=0.56 (5% triethylamine in ethylacetate); ¹H NMR (500 MHz, C₆D₆) δ 7.05-7.15 (m, 5H, ArH), 5.39 (t, 1H,J=1.5 Hz, vinyl H), 2.41 (dd, 1H, J=6, 3 Hz, ArCHN), 2.08 (m, 2H, CH₂),1.85-1.95 (m, 2H, CH₂), 1.73 (dd, 1H, J=3, 1 Hz, CH₂N), 1.60 (dd, 1H,J=6, 1 Hz, CH₂N).

Tetracyclic benzazepine 23. Cesium carbonate (66 mg, 0.20 mmol, 4.0equiv) was added to a stirred solution of aziridine 17 (10 mg, 50 μmol,1.0 equiv) in 1,4-dioxane (7.2 mL) at 25° C. The reaction vessel wassealed under argon and heated to 150° C. via oil bath for 4 d. Thereaction mixture was cooled to 25° C., gravity filtered, andconcentrated by rotary evaporation. The residue was purified by silicagel column chromatography (5% triethylamine in ethyl acetate) to afford23 (3.0 mg, 30% yield) as a white film. R_(f)=0.21 (5% triethylamine inethyl acetate); ¹H NMR (500 MHz, CD₃S(O)CD₃) δ 8.20-8.26 (m, 2H, ArH,NH), 7.13 (m, 1H, ArH), 6.97-7.05 (m, 2H, ArH), 3.40-3.50 (m, 2H, CH₂),2.88-2.94 (m, 2H, CH₂), 2.52-2.56 (m, 2H, CH₂), 2.31-2.35 (m, 2H, CH₂);¹³C NMR (125 MHz, CD₃S(O)CD₃) δ 200.32, 171.22, 138.55, 133.48, 128.62,127.20, 125.50, 124.47, 107.40, 46.52, 36.98, 33.51, 26.05; IR (neatfilm) 3251 (w, br), 2925 (w), 1574 (s), 1350 (w) cm-1; HRMS (ESI) m/z:Calcd for C₁₃H₁₄NO (MH⁺) 200.1075, observed 200.1084.

3-[2-(4-methoxy-phenyl)-aziridin-1-yl]-cyclopent-2-enone (18). Asolution of chloroenone 16 (16 mg, 0.14 mmol, 1.0 equiv) intetrahydrofuran (1.0 mL) at 25° C. was transferred via cannula to astirred solution of aziridine 14 (25 mg, 0.17 mmol, 1.2 equiv) andtriethylamine (35 μL, 0.25 mmol, 1.5 equiv) in tetrahydrofuran (1.0 mL)at 25° C. The resulting brown solution was stirred at 25° C. for 24 h.The reaction mixture was concentrated by rotary evaporation. The residuewas purified by silica gel column chromatography (5% triethylamine and20% ethyl acetate in benzene) to afford 18 (5 mg, 16% yield) as a yellowfilm. R_(f)=0.29 (5% triethylamine and 20% ethyl acetate in benzene); ¹HNMR (500 MHz, C₆D₆) δ 7.00 (m, 2H, ArH), 6.76 (m, 2H, ArH), 5.43 (t, 1H,J=1.5 Hz, vinyl H), 3.28 (s, 3H, OCH₃), 2.45 (dd, 1H, J=6, 3 Hz, ArCHN),2.11 (m, 2H, CH₂), 1.85-2.00 (m, 2H, CH₂), 1.77 (dd, 1H, J=3, 1 Hz,CH₂N), 1.63 (dd, 1H, J=6, 1 Hz, CH₂N).

Tetracyclic benzazepine 24. Cesium carbonate (30 mg, 87 μmol, 4.0 equiv)was added to a stirred solution of aziridine 18 (5.0 mg, 22 μmol, 1.0equiv) in 1,4-dioxane (3.0 mL) at 25° C. The reaction vessel was sealedunder argon and heated to 150° C. via oil bath for 4 d. The reactionmixture was cooled to 25° C., gravity filtered, and concentrated byrotary evaporation. The residue was purified by silica gel columnchromatography (10% methanol in chloroform) to afford 24 (2.6 mg, 52%yield) as a yellow film. R_(f)=0.28 (10% methanol in chloroform); ¹H NMR(500 MHz, CDCl₃) δ 8.00 (d, 1H, J=3 Hz, ArH), 6.90 (d, 1H, J=8 Hz, ArH),6.64 (dd, 1H, J=8, 3 Hz, ArH), 5.79 (br s, 1H, NH), 3.82 (s, 3H, OCH₃),3.58 (m, 2H, CH₂), 2.95 (m, 2H, CH₂), 2.50-2.60 (m, 4H, CH₂); ¹³C NMR(125 MHz, CDCl₃) δ 202.31, 170.54, 158.31, 153.19, 133.90, 131.05,129.64, 112.60, 112.04, 55.41, 48.10, 36.58, 34.03, 27.20; IR (neatfilm) 3256 (w, br), 3086 (w), 2927 (w), 1576 (s), 1512 (m), 1248 (m)cm⁻¹; HRMS (ESI) m/z: Calcd for C₁₄H₁₆NO₂ (MH⁺) 230.1181, observed230.1188.

Aziridine 19. A solution of chloroenone 16 (98 mg, 0.84 mmol, 1.2 equiv)in tetrahydrofuran (2.5 mL) at 25° C. was transferred via cannula to astirred solution of aziridine 15 (110 mg, 0.70 mmol, 1.0 equiv) andtriethylamine (0.20 mL, 1.4 mmol, 2.0 equiv) in tetrahydrofuran (2.5 mL)at 25° C. The resulting brown solution was stirred at 25° C. for 24 h.The reaction mixture was concentrated by rotary evaporation. The residuewas purified by silica gel column chromatography (5% triethylamine and20% ethyl acetate in benzene) to afford 19 (32 mg, 26% yield) as ayellow film. R_(f)=0.28 (10% methanol in chloroform); ¹H NMR (500 MHz,CDCl₃) δ 8.00 (d, 1H, J=3 Hz, ArH), 6.90 (d, 1H, J=8 Hz, ArH), 6.64 (dd,1H, J=8, 3 Hz, ArH), 5.79 (br s, 1H, NH), 3.82 (s, 3H, OCH₃), 3.58 (m,2H, CH₂), 2.95 (m, 2H, CH₂), 2.50-2.60 (m, 4H, CH₂); ¹³C NMR (125 MHz,CDCl₃) δ 202.31, 170.54, 158.31, 153.19, 133.90, 131.05, 129.64, 112.60,112.04, 55.41, 48.10, 36.58, 34.03, 27.20; IR (neat film) 3256 (w, br),3086 (w), 2927 (w), 1576 (s), 1512 (m), 1248 (m) cm⁻¹; HRMS (ESI) m/z:Calcd for C₁₄H₁₆NO₂ (MH⁺) 230.1181, observed 230.1188.

Tetracyclic benzazepine 25. Cesium carbonate (170 mg, 0.51 mmol, 4.0equiv) was added to a stirred solution of aziridine 19 (31 mg, 0.13mmol, 1.0 equiv) in 1,4-dioxane (19 mL) at 25° C. The reaction vesselwas sealed under argon and heated to 100° C. via oil bath for 4 d. Thereaction mixture was cooled to 25° C., gravity filtered, andconcentrated by rotary evaporation. The residue was purified by silicagel column chromatography (10% methanol in chloroform) to afford 25 (21mg, 68% yield) as a tan amorphous solid. R_(f)=0.43 (10% methanol inchloroform); ¹H NMR (500 MHz, CDCl₃) δ 7.85 (s, 1H, ArH), 6.53 (s, 1H,ArH), 5.91 (s, 2H, OCH₂O), 5.37 (s, 1H, NH), 3.61 (br s, 2H, CH₂), 2.93(m, 2H, CH₂), 2.56 (m, 4H, CH₂); ¹³C NMR (125 MHz, CDCl₃) δ 202.06,169.13, 146.07, 145.29, 132.39, 126.19, 110.34, 108.83, 108.57, 100.79,48.20, 37.00, 33.77, 27.06; IR (neat film) 3260 (w, br), 3074 (w), 2923(w), 1557 (s), 1244 (m), 1038 (m) cm⁻¹; HRMS (EI) m/z: Calcd forC₁₄H₁₃NO₃ (M⁺) 243.0895, observed 243.0895.

2-(2-Benzo[1,3]dioxol-5-yl-aziridin-1-yl)-but-2-enedioic acid dimethylester (26). Dimethyl acetylene dicarboxylate (75 μL, 0.61 mmol, 1.0equiv) was added via syringe to a stirred solution of aziridine 15 (100mg, 0.61 mmol, 1.0 equiv) in tetrahydrofuran (1.0 mL) at 25° C. Theresulting bright yellow solution was stirred at 25° C. for 2 d. Thereaction mixture was concentrated by rotary evaporation. The residue waspurified by silica gel column chromatography (1% triethylamine and 24%ethyl acetate in benzene) to afford 26 (110 mg, 57% yield, 3:1 E:Zmixture) as a yellow film. E-26: R_(f)=0.31 (1% triethylamine and 24%ethyl acetate in benzene); ¹H NMR (500 MHz, C₆D₆) δ 6.64 (m, 1H, ArH),6.52-6.54 (m, 2H, ArH), 5.30 (s, 1H, vinyl H), 5.22-5.25 (m, 2H, OCH₂O),3.52 (s, 3H, OCH₃), 3.34 (s, 3H, OCH₃), 2.84 (dd, 1H, J=6, 3.5 Hz,ArCHN), 1.84 (d, 1H, J=6 Hz, CH₂N), 1.71 (d, 1H, J=3.5 Hz, CH₂N).

4-Benzo[1,3]dioxol-5-yl-1H-pyrrole-2,3-dicarboxylic acid dimethyl ester(27). Cesium carbonate (110 mg, 0.30 mmol, 4.0 equiv) was added to astirred solution of aziridine 26 (25 mg, 82 μmol, 1.0 equiv) in1,4-dioxane (12 mL) at 25° C. The reaction vessel was sealed under argonand heated to 100° C. via oil bath for 20 h. The reaction mixture wascooled to 25° C., gravity filtered, and concentrated by rotaryevaporation to afford 27 (23 mg, 92% yield) as a dark orange film. ¹HNMR (500 MHz, CDCl₃) δ 10.22 (br d, 1H, J=11 Hz, NH), 7.43 (dd, 1H,J=14, 11 Hz, pyrrole H), 6.80 (d, 1H, J=1.5 Hz, ArH), 6.72 (d, 1H, J=8Hz, ArH), 6.69 (dd, 1H, J=8, 1.5 Hz, ArH), 5.93 (s, 2H, OCH₂O), 3.89 (s,3H, OCH₃), 3.73 (s, 3H, OCH₃); IR (neat film) 3348 (w, br), 2944 (w),2890 (w), 1731 (m), 1651 (s), 1608 (s), 1503 (m), 1484 (m), 1444 (m)cm⁻¹; HRMS (ESI) m/z: Calcd for C₁₅H₁₄NO₆ (MH⁺) 304.0821, observed304.0815.

3-(2-Benzo[1,3]dioxol-5-yl-2-chloro-ethylamino)-cyclopent-2-enone (30).A solution of chloroenone 16 (98 mg, 0.84 mmol, 1.2 equiv) intetrahydrofuran (2.5 mL) at 25° C. was transferred via cannula to astirred solution of aziridine 15 (110 mg, 0.70 mmol, 1.0 equiv) andtriethylamine (0.20 mL, 1.4 mmol, 2.0 equiv) in tetrahydrofuran (2.5 mL)at 25° C. The reaction vessel was sealed under argon and heated to 60°C. via oil bath for 24 h. The reaction mixture was cooled to 25° C. andconcentrated by rotary evaporation. The residue was purified by silicagel column chromatography (7% triethylamine in ethyl acetate) to afford30 (120 mg, 64% yield) as a yellow film. R_(f)=0.13 (5% triethylamine inethyl acetate); ¹H NMR (500 MHz, C₆D₆) δ 6.64 (d, 1H, J=2 Hz, ArH), 6.47(d, 1H, J=8 Hz, ArH), 6.31 (dd, 1H, J=8, 2 Hz, ArH), 5.24 (d, 1H, J=1.5Hz, OCH₂O), 5.22 (d, 1H, J=1.5 Hz, OCH₂O), 4.99 (s, 1H, vinyl H), 4.51(br s, 1H, CHCl), 3.92 (br s, 1H, NH), 2.93 (m, 2H, CH₂), 2.14 (t, 2H,J=5.5 Hz, CH₂), 1.62 (m, 2H, CH₂); IR (neat film) 3242 (w, br), 3061(w), 2915 (w), 1565 (s), 1504 (m), 1490 (m), 1445 (m), 1251 (m), 1187(w), 1038 (m) cm⁻¹; HRMS (EI) m/z: Calcd for C₁₄H₁₅NO₃Cl(MH⁺) 280.0740,observed 280.0740.

Tetracyclic benzazepine 25. Cesium carbonate (170 mg, 0.50 mmol, 4.0equiv) was added to a stirred solution of chloride 30 (35 mg, 0.13 mmol,1.0 equiv) in 1,4-dioxane (18 mL) at 25° C. The reaction vessel wassealed under argon and heated to 100° C. via oil bath for 4 d. Thereaction mixture was cooled to 25° C., gravity filtered, andconcentrated by rotary evaporation. The residue was purified by silicagel column chromatography (10% methanol in chloroform) to afford 25 (20mg, 67% yield) as a tan amorphous solid. R_(f)=0.43 (10% methanol inchloroform); ¹H NMR (500 MHz, CDCl₃) δ 7.85 (s, 1H, ArH), 6.53 (s, 1H,ArH), 5.91 (s, 2H, OCH₂O), 5.37 (s, 1H, NH), 3.61 (br s, 2H, CH₂), 2.93(m, 2H, CH₂), 2.56 (m, 4H, CH₂); ¹³C NMR (125 MHz, CDCl₃) δ 202.06,169.13, 146.07, 145.29, 132.39, 126.19, 110.34, 108.83, 108.57, 100.79,48.20, 37.00, 33.77, 27.06; IR (neat film) 3260 (w, br), 3074 (w), 2923(w), 1557 (s), 1244 (m), 1038 (m) cm⁻¹; HRMS (EI) m/z: Calcd forC₁₄H₁₃NO₃ (M⁺) 243.0895, observed 243.0895.

N-(Trimethylsilyl)methyl benzazepine 31. 60% sodium hydride in mineraloil (39 mg, 0.96 mmol, 1.3 equiv) was added to a stirred solution ofbenzazepine 25 (180 mg, 0.74 mmol, 1.0 equiv) in tetrahydrofuran (9.3mL) at 25° C. The resulting brown suspension was stirred at 25° C. for 1h. (Iodomethyl)trimethylsilane (0.55 mL, 3.7 mmol, 5.0 equiv) was addedvia syringe at 25° C. The reaction vessel was sealed under argon andheated to 50° C. via oil bath for 30 m. The reaction mixture was cooledto 25° C. and approximately 50% of the solvent volume was removed bysweeping with nitrogen. The crude reaction mixture was loaded directlyonto a column and purified by silica gel column chromatography (5%triethylamine in ethyl acetate) to afford 31 (151 mg, 62% yield) as anoff-white amorphous solid. R_(f)=0.41 (5% triethylamine in ethylacetate); ¹H NMR (500 MHz, CDCl₃) δ 7.76 (s, 1H, ArH), 6.48 (s, 1H,ArH), 5.89 (s, 2H, OCH₂O), 3.56 (m, 2H, CH₂), 3.02 (br s, 2H, NCH₂Si),2.91 (m, 2H, CH₂), 2.59 (m, 2H, CH₂), 2.49 (m, 2H, CH₂), 0.13 (s, 9H,Si(CH₃)₃); ¹³C NMR (125 MHz, CDCl₃) δ 200.86, 169.37, 146.18, 145.19,132.71, 127.17, 110.46, 109.47, 108.06, 100.92, 57.78, 46.78, 36.22,33.37, 28.08, −1.26; IR (neat film) 2953 (w, br), 1647 (w), 1556 (s),1488 (m), 1445 (m), 1353 (w), 1248 (m), 1039 (m), 843 (m) cm⁻¹; HRMS(EI) m/z: Calcd for C₁₈H₂₃NO₃Si (MH⁺) 330.1525, observed 330.1525.

Pentacyclic enol trifluoromethanesulfonate 33. Trifluoromethanesulfonicanhydride (5.0 μL, 30 μmol, 1.1 equiv) was added to a stirred solutionof vinylogous amide 31 (9.0 mg, 27 μmol, 1.0 equiv) in dichloromethane(0.40 mL) at 25° C. The resulting dark orange solution was stirred at25° C. for 30 m. Dimethyl acetylenedicarboxylate (4.8 μL, 39 μmol, 1.4equiv) and tetrabutylammonium triphenyldifluorosilicate (16 mg, 30 μmol,1.1 equiv) were sequentially added at 25° C. The resulting dark purplemixture was stirred at 25° C. for 24 h. The crude reaction mixture wasloaded directly onto a column and purified by silica gel columnchromatography (50% hexane in ethyl acetate) to afford 33 (7.7 mg, 53%yield) as a colorless film. R_(f)=0.44 (50% hexane in ethyl acetate); ¹HNMR (500 MHz, CDCl₃) δ 6.58 (s, 2H, ArH), 5.95 (d, 1H, J=1.5 Hz, OCH₂O),5.91 (d, 1H, J=1.5 Hz, OCH₂O), 3.95 (s, 2H, NCH₂C), 3.76 (s, 3H, OCH₃),3.70 (s, 3H, OCH₃), 3.54 (ddd, 1H, J=15, 11, 4 Hz, CH₂), 3.22 (ddd, 1H,J=16, 11, 5 Hz, CH₂), 3.03 (ddd, 1H, J=15, 5, 2 Hz, CH₂), 2.96 (m, 1H,CH₂), 2.77 (ddd, 1H, J=16, 10, 3 Hz, CH₂), 2.65 (m, 1H, CH₂), 2.54 (ddd,1H, J=13, 9, 3 Hz, CH₂), 2.16 (ddd, 1H, J=13, 9, 6 Hz, CH₂).

7a-(2-Iodo-but-1-enyl)-5,6,7,7a-tetrahydro-3H-pyrrolizine-1,2-dicarboxylicacid dimethyl ester (40). To a stirred solution of1-(1-trimethylsilanylmethyl-pyrrolidi-2-ylidene)-butan-2-one (39) (49.6mg, 0.220 mmol, 1.0 equiv) in dry dichloromethane (3 mL) at roomtemperature was added via syringe trifluoromethanesulfonic anhydride (41μL, 0.24 mmol, 1.1 equiv). The resulting yellow solution was stirred for15 minutes before the addition of dimethylacetylene dicarboxylate (135μL, 1.10 mmol, 5.0 equiv) and tetrabutylammonium iodide (89.0 mg, 0.242mmol, 1.1 equiv). The resulting dark amber solution was then stirred atroom temperature for 10 minutes before the addition oftetrabutylammonium triphenyldifluorosilicate (131 mg, 0.242 mmol, 1.0equiv). The resulting dark red solution was stirred at room temperaturefor 22 h and then concentrated in vacuo. Purification by silica gelflash chromatography (33% ethyl acetate in hexanes) provided 40 (46.6mg, 52%, (Z)-isomer only) as a bright yellow oil. (Z)-isomer; R_(f)=0.41(33% ethyl acetate in hexanes); ¹H NMR (500 MHz, C₆D₆) δ 6.04 (s, 1 H,vinyl H), 4.40 (d, 1 H, J=16.8 Hz, NCH₂), 3.48 (d, 1 H, J=16.8 Hz,NCH₂), 3.47 (s, 3 H, CO₂CH₃), 3.31 (s, 3 H, CO₂CH₃), 3.02 (dt, 1 H,J=9.8, 5.7 Hz, NCH₂CH₂CH₂), 2.35 (qd, 2 H, J=7.4, 1.1 Hz, CH₂CH₃), 2.26(dt, 1 H, J=10.6, 6.8 Hz, NCH₂CH₂CH₂), 2.21 (m, 1 H, NCH₂CH₂CH₂), 2.05(m, 1 H, NCH₂CH₂CH₂), 1.55 (m, 1 H, NCH₂CH₂CH₂), 1.44 (m, 1 H,NCH₂CH₂CH₂), 0.92 (t, 3 H, J=7.3 Hz, CH₂CH₃); FTIR (neat film, NaCl)2967, 1722 (C═O), 1652, 1435, 1272, 1198, 1102 cm⁻¹; HRMS (FAB) m/z:Calcd for C₁₅ H₂₁N₁O₄I₁ (M+H)⁺ 406.0515, found 406.0517.

7a-(2-Bromo-but-1-enyl)-5,6,7,7a-tetrahydro-3H-pyrrolizine-1,2-dicarboxylicacid dimethyl ester (41). To a stirred solution of1-(1-trimethylsilanylmethyl-pyrrolidi-2-ylidene)-butan-2-one (39) (32.5mg, 0.144 mmol, 1.0 equiv) in dry dichloromethane (2 mL) at roomtemperature was added via syringe trifluoromethanesulfonic anhydride (27μL, 0.16 mmol, 1.1 equiv). The resulting yellow solution was stirred for10 minutes before the addition of dimethylacetylene dicarboxylate (89μL, 0.72 mmol, 5.0 equiv) and tetrabutylammonium bromide (102 mg, 0.317mmol, 2.2 equiv). The resulting dark amber solution was then stirred atroom temperature for 12 h before the addition of tetrabutylammoniumtriphenyldifluorosilicate (86.4 mg, 0.159 mmol, 1.0 equiv). Theresulting dark red solution was stirred at room temperature for 1 h andthen concentrated in vacuo. Purification by silica gel flashchromatography (50% ethyl acetate in hexanes) provided 41 (23.3 mg, 45%,(4-isomer only) as a bright yellow oil. (Z)-isomer; R_(f)=0.38 (50%ethyl acetate in hexanes); ¹ H NMR (500 MHz, C₆D₆) δ 6.06 (s, 1 H, vinylH), 4.32 (d, 1 H, J=16.7 Hz, NCH₂), 3.52 (s, 3 H, CO₂CH₃), 3.45 (d, 1 H,J=16.7 Hz, NCH₂), 3.30 (s, 3 H, CO₂CH₃), 2.96 (dt, 1 H, J=9.7, 5.7 Hz,NCH₂CH₂CH₂), 2.43 (dt, 1 H, J=13.0, 7.5 Hz, NCH₂CH₂CH₂), 2.23 (m, 4 H,NCH₂CH₂CH₂ and CH₂CH₃), 1.54 (m, 1 H, NCH₂CH₂CH₂), 1.45 (m, 1 H,NCH₂CH₂CH₂), 0.92 (t, 3 H, J=7.3 Hz, CH₂CH₃); FTIR (neat film, NaCl)2950, 1721 (C═O), 1654, 1434, 1271, 1197, 1135 cm⁻¹; HRMS (FAB) m/z:Calcd for C₁₅ H₂₁N₁O₄Br₁ (M+H)⁺ 358.0654, found 358.0653.

7a-(2-Chloro-but-1-enyl)-5,6,7,7a-tetrahydro-3H-pyrrolizine-1,2-dicarboxylicacid dimethyl ester (42). To a stirred solution of1-(1-trimethylsilanylmethyl-pyrrolidi-2-ylidene)-butan-2-one (39) (34.7mg, 0.154 mmol, 1.0 equiv) in dry dichloromethane (2 mL) at roomtemperature was added via syringe trifluoromethanesulfonic anhydride (28μL, 0.17 mmol, 1.1 equiv). The resulting yellow solution was stirred for10 minutes before the addition of dimethylacetylene dicarboxylate (95μL, 0.77 mmol, 5.0 equiv) and tetrabutylammonium chloride (94.2 mg,0.339 mmol, 2.2 equiv). The resulting dark orange solution was thenstirred at room temperature for 4 h before the addition oftetrabutylammonium triphenyldifluorosilicate (91.1 mg, 0.169 mmol, 1.0equiv). The dark red solution was stirred at room temperature for 1 hand then concentrated in vacuo. Purification by silica gel flashchromatography (33% hexanes in ethyl acetate) provided 42 (25.1 mg, 52%,(Z)-isomer only) as a bright yellow oil. (Z)-isomer; R_(f)=0.42 (33%hexanes in ethyl acetate); ¹ H NMR (500 MHz, C₆D₆) δ 5.79 (s, 1 H, vinylH), 4.28 (d, 1 H, J=16.7 Hz, NCH₂), 3.53 (s, 3 H, CO₂CH₃), 3.44 (d, 1 H,J=16.7 Hz, NCH₂), 3.29 (s, 3H, CO₂CH₃), 2.95 (dt, 1 H, J=9.7, 5.7 Hz,NCH₂CH₂CH₂), 2.48 (dt, 1 H, J=13.1, 7.5 Hz, NCH₂CH₂CH₂), 2.21 (m, 2 H,NCH₂CH₂CH₂), 2.07 (q, 2 H, J=7.3 Hz, CH₂CH₃), 1.53 (m, 1 H, NCH₂CH₂CH₂),1.45 (m, 1 H, NCH₂CH₂CH₂), 0.91 (t, 3 H, J=7.3 Hz, CH₂CH₃); FTIR (neatfilm, NaCl) 2951, 1722 (C═O), 1652, 1435, 1271, 1197, 1130, 1102 cm⁻¹;HRMS (FAB) m/z: Calcd for C₁₅ H₂₁N₁O₄Cl₁ (M+H)⁺ 314.1159, found314.1159.

Pentacyclic enol benzoate 43. Trifluoromethanesulfonic anhydride (12 μL,70 μmol, 1.1 equiv) was added to a stirred solution of vinylogous amide31 (21 mg, 64 μmol, 1.0 equiv) in dichloromethane (0.50 mL) at 25° C.The resulting dark orange solution was stirred at 25° C. for 30 m. Thesolution was transferred via cannula to a stirred suspension of benzoicacid (8.6 mg, 70 μmol, 1.1 equiv) and cesium carbonate (25 mg, 76 μmol,1.2 equiv) in dichloromethane (0.40 mL) at 25° C. The resulting darkbrown mixture was stirred at 25° C. for 30 m. Dimethylacetylenedicarboxylate (40 μL, 0.32 mmol, 5.0 equiv) andtetrabutylammonium triphenyldifluorosilicate (25 mg, 76 μmol, 1.2 equiv)were sequentially added at 25° C. The dark brown mixture was stirred at25° C. for 24 h. The crude reaction mixture was loaded directly onto acolumn and purified by silica gel column chromatography (50% hexane inethyl acetate) to afford 43 (8.0 mg, 64% yield) as a pale yellow film.R_(f)=0.32 (50% hexane in ethyl acetate); ¹H NMR (500 MHz, CDCl₃) δ 8.01(m, 2H, Ph), 7.57 (m, 1H, Ph), 7.44 (m, 2H, Ph), 6.62 (s, 1H, ArH), 6.54(s, 1H, ArH), 5.90 (d, 1H, J=1.5 Hz, OCH₂O), 5.87 (d, 1H, J=1.5 Hz,OCH₂O), 3.98 (br d, 2H, J=2.8 Hz, NCH₂C), 3.80 (s, 3H, OCH₃), 3.75 (m,1H, CH₂), 3.70 (s, 3H, OCH₃), 3.24 (ddd, 1H, J=15, 11, 5 Hz, CH₂), 3.03(ddd, 1H, J=15, 5, 3 Hz, CH₂), 2.96 (m, 1H, CH₂), 2.77 (ddd, 1H, J=14,10, 3 Hz, CH₂), 2.65 (m, 1H, CH₂), 2.58 (m, 1H, CH₂), 2.18 (m, 1H, CH₂);IR (neat film) 2949 (w, br), 1732 (s), 1484 (m), 1264 (s) cm⁻¹; HRMS(FAB) m/z: Calcd for C₂₈H₂₆NO₈ (MH⁺) 504.1656, observed 504.1658.

2-(3-Methyl-butyl)-2-triethylsilanyloxy-succinic acid 4-methyl ester(44). 10% Palladium on carbon (2 mg, ˜10 wt. %) was added to a stirredsolution of benzyl ester S2 (21 mg, 0.50 mmol, 1.0 equiv) in ethylacetate (1.0 mL) at 25° C. The resulting black mixture was charged withan atmosphere of hydrogen (balloon) and stirred at 25° C. for 24 h. Thecrude reaction mixture was eluted through a short plug of celite (120 mLethyl acetate) and the organic layer was concentrated by rotaryevaporation to afford 44 (12 mg, 73% yield) as a colorless film.R_(f)=0.01 (17% ethyl acetate in hexane); ¹H NMR (500 MHz, CDCl₃) δ 3.72(br s, 1H, COOH), 3.66 (s, 3H, COOCH₃), 2.90 (d, 1H, J=6 Hz,CH₃OOCCH₂C), 2.69 (d, 1H, J=6 Hz, CH₃OOCCH₂C), 1.67 (m, 2H,CCH₂CH₂CH(CH₃)₂), 1.50 (hep, 1H, J=6.5 Hz, CCH₂CH₂CH(CH₃)₂), 1.40 (m,2H, CCH₂CH₂CH(CH₃)₂), 0.99 (t, 9H, J=8 Hz, OSi(CH₂CH₃)₃), 0.80-0.90 (m,12H, CCH₂CH₂CH(CH₃)₂, OSi(CH₂CH₃)₃); IR (neat film) 3507 (w), 2956 (s),1744 (s), 1219 (s), 741 (s) cm⁻¹.

2-(tert-Butyl-dimethyl-silanyloxy)-1-(2,2-dimethyl-5-vinyl-[1,3]dioxolan-4-yl)-ethanol(S3). Methyltriphenylphosphonium bromide (37 g, 100 mmol, 1.2 equiv) wasadded to a stirred solution of 95% potassium bis(trimethylsilyl)amide(18 g, 83 mmol, 1.0 equiv) in tetrahydrofuran (270 mL) at 0° C. Theresulting yellow mixture was stirred at 0° C. for 2 h. A solution ofhemiacetal 48 (26 g, 84 mmol, 1.0 equiv) in tetrahydrofuran (150 mL) wastransferred via cannula to the reaction mixture at 0° C. The resultingoff-white mixture was stirred at 0° C. for 30 min. The reaction vesselwas equipped with a reflux condenser and heated to 60° C. via oil bathfor 2 d. The reaction mixture was cooled to 25° C., diluted with diethylether (400 mL), washed with water (1×400 mL), and washed with asaturated solution of sodium chloride (1×400 mL). The organic layer wasdried (magnesium sulfate), gravity filtered, and concentrated by rotaryevaporation. The residue was purified by silica gel columnchromatography (14% ethyl acetate in hexane) to afford S3 (19 g, 75%yield) as a colorless oil. R_(f)=0.35 (14% ethyl acetate in hexane); ¹HNMR (500 MHz, C₆D₆) δ 6.20 (ddd, 1H, J=5, 10.5, 17 Hz, CHCH₂), 5.51(ddd, 1H, J=1.5, 2, 17 Hz, CHCH₂), 5.19 (ddd, 1H, J=1.5, 2, 10.5 Hz,CHCH₂), 4.72 (m, 1H, CH(OR)), 4.10 (dd, 1H, J=6.5, 9 Hz, CH(OR)), 3.83(m, 1H, CH(OH)), 3.72-3.77 (m, 2H, CH₂(OTBS)), 1.44 (s, 3H, CH₃), 1.27(s, 3H, CH₃), 0.89 (s, 9H, C(CH₃)₃), 0.00 (s, 3H, SiCH₃), −0.01 (s, 3H,SiCH₃); ¹³C NMR (125 MHz, C₆D₆) δ 135.25, 116.57, 108.86, 78.97, 77.95,70.30, 65.24, 28.07, 26.06, 25.60, 18.54, −5.28, −5.37; IR (neat film)3505 (w), 2931 (m), 2858 (m) cm⁻¹; HRMS (ESI) m/z: Calcd forC₁₅H₃₀NaO₄Si (MNa⁺) 325.1811, observed 325.1824.

2-(tert-Butyl-dimethyl-silanyloxy)-1-(2,2-dimethyl-5-vinyl-[1,3]dioxolan-4-yl)-ethanone(49). Dimethylsulfoxide (7.0 mL, 99 mmol, 30 equiv), triethylamine (2.8mL, 20 mmol, 6.0 equiv), and sulfur trioxide-pyridine complex (3.2 g, 20mmol, 6.0 equiv) were sequentially added to a stirred solution ofalcohol S3 (1.0 g, 3.3 mmol, 1.0 equiv) in dichloromethane (185 mL) at0° C. The resulting colorless solution was stirred at 0° C. for 15 min,warmed to 25° C., and stirred for 45 min. The reaction mixture wasdiluted with water (100 mL) and extracted with diethyl ether (3×80 mL).The combined organic layers were dried (magnesium sulfate), gravityfiltered, and concentrated by rotary evaporation. The residue waspurified by silica gel column chromatography (12.5% ethyl acetate inhexane) to afford 49 (870 mg, 88% yield) as a colorless oil. R_(f)=0.41(12.5% ethyl acetate in hexane); ¹H NMR (500 MHz, C₆D₆) δ 5.70 (ddd, 1H,J=5.5, 10.5, 17 Hz, CHCH₂), 5.51 (dt, 1H, J=1.5, 17 Hz, CHCH₂), 5.19(dt, 1H, J=1.5, 10.5 Hz, CHCH₂), 4.50-4.56 (m, 3H, CH(OR), CH(OR),CH₂(OTBS)), 4.30 (d, 1H, J=19 Hz, CH₂(OTBS)), 1.47 (s, 3H, CH₃), 1.09(s, 3H, CH₃), 0.96 (s, 9H, C(CH₃)₃), 0.05 (s, 3H, SiCH₃), 0.04 (s, 3H,SiCH₃); ¹³C NMR (125 MHz, C₆D₆) δ 205.42, 133.27, 117.84, 110.36, 82.21,78.48, 69.07, 26.93, 26.01, 24.69, 18.60, −5.16, −5.21; IR (neat film)2930 (m), 2858 (m), 1739 (m) cm⁻¹; HRMS (ESI) m/z: Calcd forC₁₅H₂₈NaO₄Si (MNa⁺) 323.1655, observed 323.1676.

2-(tert-Butyl-dimethyl-silanyloxy)-2-(2,2-dimethyl-5-vinyl-[1,3]dioxolan-4-yl)-but-3-en-2-ol(50). A 1 molar solution of vinyl bromide in tetrahydrofuran (26 mL, 26mmol, 2.2 equiv) was added dropwise to a mixture of magnesium turnings(570 mg, 23 mmol, 2.0 equiv) in tetrahydrofuran at 25° C. The resultingmixture was stirred at 25° C. for 16 h (the mixture began to turnhomogeneous brown and spontaneously reflux after 30 min). The solutionof vinyl magnesium bromide in tetrahydrofuran was transferred viacannula to a stirred solution of ketone 49 (3.5 g, 12 mmol, 1.0 equiv)in tetrahydrofuran (35 mL) at −78° C. The resulting brown solution wasstirred at −78° C. for 1.5 h, warmed to 25° C., and stirred for 30 min.The reaction mixture was cooled to −78° C., quenched with a saturatedsolution of ammonium chloride (20 mL), diluted with water (100 mL), andextracted with ethyl acetate (3×100 mL). The combined organic layerswere dried (magnesium sulfate), gravity filtered, and concentrated byrotary evaporation. The residue was purified by passage through a plugof silica gel (dichloromethane) to afford 50 (3.5 g, 93% yield) as acolorless oil consisting of a 8:1 mixture of inseperable diastereomers.R_(f)=0.54 (12.5% ethyl acetate in hexane); ¹H NMR (500 MHz, C₆D₆) δ6.41 (ddd, 1H, J=5.5, 10.5, 17 Hz, CHCH₂), 6.27 (ddd, 1H, J=0.5, 12,17.5 Hz, CHCH₂), 5.61 (dd, 1H, J=2, 17.5 Hz, CHCH₂), 5.37 (ddd, 1H,J=1.5, 2, 17 Hz, CHCH₂), 5.21 (ddd, 1H, J=0.5, 2, 12 Hz, CHCH₂), 5.10(ddd, 1H, J=1.5, 2, 10.5 Hz, CHCH₂), 4.72 (m, 1H, CH(OR)), 4.41 (d, 1H,J=7 Hz, CH(OR)), 3.83 (d, 1H, J=10 Hz, CH₂(OTBS)), 3.44 (d, 1H, J=10 Hz,CH₂(OTBS)), 2.68 (d, 1H, J=0.6 Hz, OH), 1.48 (s, 3H, CH₃), 1.28 (s, 3H,CH₃), 0.89 (s, 9H, C(CH₃)₃), −0.01 (s, 3H, SiCH₃), −0.03 (s, 3H, SiCH₃);¹³C NMR (125 MHz, C₆D₆) δ 138.56, 136.34, 116.35, 115.88, 108.30, 79.42,78.55, 75.58, 68.99, 27.53, 26.00, 25.04, 18.51, −5.35, −5.45; IR (neatfilm) 3557 (w), 2955 (m), 2859 (m) cm⁻¹; HRMS (ESI) m/z: Calcd forC₁₇H₃₂NaO₄Si (MNa⁺) 351.1968, observed 351.1966.

4-(tert-Butyl-dimethyl-silanyloxymethyl)-2,2-dimethyl-4,6adihydro-3aH-cyclopenta[1,3]-dioxol-4-ol(51). A stirred solution of diene 50 (6:1 dr) (9.4 g, 29 mmol, 1.0equiv) in dichloromethane (300 mL) was subjected to two freeze-pump-thawcycles. Grubbs 2^(nd) generation catalyst (490 mg, 0.57 mmol, 0.02equiv) was added at 25° C. The resulting purple solution was subjectedto one freeze-pump-thaw cycle. The purple solution was stirred at 25° C.for 24 h. The reaction mixture was concentrated by rotary evaporation.The residue was purified by silica gel column chromatography (12.5%ethyl acetate in hexane) to afford 51 (6.8 g, 95% yield based on 6:1 drof 50) as a brown oil. R_(f)=0.23 (12.5% ethyl acetate in hexane); ¹HNMR (500 MHz, C₆D₆) δ 5.80 (dd, 1H, J=2, 6 Hz, HCCH), 5.66 (d, 1H, J=6Hz, HCCH), 5.19 (br d, 1H, J=6 Hz, CH(OR)), 4.55 (d, 1H, J=6 Hz,CH(OR)), 4.03 (d, 1H, J=10 Hz, CH₂(OTBS)), 3.69 (d, 1H, J=10 Hz,CH₂(OTBS)), 3.06 (s, 1H, OH), 1.36 (s, 3H, CH₃), 1.21 (s, 3H, CH₃), 0.91(s, 9H, C(CH₃)₃), 0.03 (s, 3H, SiCH₃), 0.01 (s, 3H, SiCH₃); ¹³C NMR (125MHz, C₆D₆) δ 135.48, 135.25, 112.07, 85.42, 85.16, 84.87, 65.77, 27.82,26.13, 26.05, 18.58, −5.34; IR (neat film) 3541 (w), 2931 (m), 2858 (m)cm⁻¹; HRMS (ESI) m/z: Calcd for C₁₅H₂₈NaO₄Si (MNa⁺) 323.1655, observed323.1650.

4-(tert-Butyl-dimethyl-silanyloxymethyl)-6-chloro-2,2-dimethyl-5-phenylselanyl-tetrahydro-cyclopenta[1,3]-dioxol-4-ol(S4). Phenylselenenyl chloride (4.0 mg, 21 mmol, 1.1 equiv) was added toa stirred solution of alkene 51 (6.0 g, 20 mmol, 1.0 equiv) inacetonitrile (100 mL) at 0° C. The resulting orange solution was stirredat 0° C. for 1 h. The reaction mixture was concentrated by rotaryevaporation to afford S4 (10 g, 99% yield) as an orange oil. R_(f)=0.36(10% ethyl acetate in hexane); ¹H NMR (500 MHz, C₆D₆) δ 7.48-7.51 (m,2H, SePh), 6.90-6.96 (m, 3H, SePh), 4.95 (dt, 1H, J=1, 6 Hz, CH(OR)),4.88 (dd, 1H, J=1, 2 Hz, CHCl), 4.43 (dd, 1H, J=2, 6 Hz, CH(OR)), 4.17(d, 1H, J=10 Hz, CH₂(OTBS)), 4.00 (d, 1H, J=10 Hz, CH₂(OTBS)), 3.92 (m,1H, CHSePh), 3.19 (s, 1H, OH), 1.56 (s, 3H, CH₃), 1.04 (s, 3H, CH₃),0.88 (s, 9H, C(CH₃)₃), 0.02 (s, 3H, SiCH₃), 0.01 (s, 3H, SiCH₃); ¹³C NMR(125 MHz, C₆D₆) δ 132.79, 131.81, 129.48, 127.42, 112.09, 89.08, 85.72,84.19, 69.35, 65.41, 56.79, 25.83, 25.77, 23.87, 18.30, −5.48, −5.62; IR(neat film) 3527 (w), 2930 (m), 2857 (m) cm⁻¹.

4-(tert-Butyl-dimethyl-silanyloxymethyl)-6-chloro-2,2-dimethyl-4,6a-dihydro-3aH-cyclopenta[1,3]-dioxol-4-ol(52). 70% meta-Chloroperoxybenzoic acid (6.4 g, 26 mmol, 1.3 equiv) wasadded to a stirred solution of selenide S4 (9.8 g, 20 mmol, 1.0 equiv)in dichloromethane (100 mL) at 0° C. The resulting orange mixture wasstirred at 0° C. for 5 h. Dimethyl sulfide (19 mL, 260 mmol, 13 equiv)was added at 0° C. The resulting light brown mixture was stirred at 0°C. for 30 min. Triethylamine (5.6 mL, 40 mmol, 2.0 equiv) was added at0° C. The resulting brown solution was stirred at 0° C. for 10 min,warmed to 25° C., and stirred for 1 h. The reaction mixture was dilutedwith a saturated solution of sodium bicarbonate (400 mL), and extractedwith ethyl acetate (3×300 mL). The combined organic layers were dried(magnesium sulfate), gravity filtered, and concentrated by rotaryevaporation to afford 52 (6.7 g, 99% yield) as a brown oil. R_(f)=0.32(12.5% ethyl acetate in hexane); ¹H NMR (500 MHz, C₆D₆) δ 5.63 (br s,1H, CHCCl), 4.96 (d, 1H, J=5 Hz, CH(OR)), 4.41 (dd, 1H, J=1.2, 5 Hz,CH(OR)), 3.88 (d, 1H, J=10 Hz, CH₂(OTBS)), 3.56 (d, 1H, J=10 Hz,CH₂(OTBS)), 3.15-3.35 (br s, 1H, OH), 1.32 (s, 3H, CH₃), 1.14 (s, 3H,CH₃), 0.87 (s, 9H, C(CH₃)₃), −0.02 (s, 3H, SiCH₃), −0.03 (s, 3H, SiCH₃);¹³C NMR (125 MHz, C₆D₆) δ 140.02, 131.71, 113.01, 85.36, 85.10, 82.55,65.35, 27.56, 26.28, 25.94, 18.47, −5.43, −5.48; IR (neat film) 3537(w), 2931 (m), 2858 (m), 1715 (w), 1624 (w) cm⁻¹.

6-Chloro-4-hydroxymethyl-2,2-dimethyl-4,6a-dihydro-3aH-cyclopenta[1,3]-dioxol-4-ol(S5). A 1 molar solution of tetrabutylammonium fluoride intetrahydrofuran (27 mL, 1.3 equiv) was added to a stirred solution ofsilyl ether 52 (6.7 g, 20 mmol, 1.0 equiv) in tetrahydrofuran (80 mL) at25° C. The resulting brown solution was stirred at 25° C. for 3 h. Thereaction mixture was concentrated by rotary evaporation. The residue waspurified by silica gel column chromatography (25% hexane in ethylacetate) to afford S5 (4.4 g, 99% yield) as a brown oil. R_(f)=0.44 (25%hexane in ethyl acetate); ¹H NMR (500 MHz, C₆D₆) δ 5.37 (t, 1H, J=1 Hz,CHCCl), 4.79 (dd, 1H, J=0.5, 5.5 Hz, CH(OR)), 4.23 (dd, 1H, J=1, 5.5 Hz,CH(OR)), 3.64 (d, 1H, J=11 Hz, CH₂(OH)), 3.37 (d, 1H, J=11 Hz, CH₂(OH)),1.23 (s, 3H, CH₃), 1.07 (d, 3H, J=0.6 Hz, CH₃); ¹³C NMR (125 MHz, C₆D₆)δ 139.51, 130.65, 113.46, 85.82, 85.33, 83.12, 65.29, 27.29, 26.08; IR(neat film) 3401 (m), 2989 (w), 2937 (w), 1624 (w) cm⁻¹; HRMS (ESI) m/z:Calcd for C₉H₁₃ClNaO₄ (MNa⁺) 243.0400, observed 243.0412.

6-Chloro-2,2-Dimethyl-3a,6a-dihydro-cyclopenta[1,3]dioxol-4-one (53). A0.5 molar solution of sodium periodate in water (10 mL, 5.00 mmol, 1.1equiv) was added to a stirred solution of diol S5 (1.0 g, 4.5 mmol, 1.0equiv) in dichloromethane (23 μL) at 25° C. The resulting biphasicmixture was vigorously stirred at 25° C. for 30 min. The reactionmixture was diluted with water (50 mL) and extracted withdichloromethane (3×40 mL). The combined organic layers were dried(magnesium sulfate), gravity filtered, and concentrated by rotaryevaporation. The residue was purified by silica gel columnchromatography (20% ethyl acetate in hexane) to afford 53 (750 mg, 90%yield) as a white crystalline solid. R_(f)=0.35 (25% ethyl acetate inhexane); ¹H NMR (500 MHz, C₆D₆) δ 5.54 (s, 1H, ClCCH), 4.21 (d, 1H,J=5.5 Hz, CH(OR)), 3.94 (d, 1H, J=5.5 Hz, CH(OR)); 1.19 (s, 3H, CH₃),1.10 (d, 3H, J=0.3 Hz, CH₃); ¹³C NMR (125 MHz, C₆D₆) δ 196.82, 145.39,131.16, 115.65, 81.01, 79.00, 27.30, 26.31; IR (neat film) 2987 (w),2933 (w), 1722 (s), 1582 (s) cm⁻¹; HRMS (EI) m/z: Calcd for C₈H₉ClO₃(M⁺) 188.0240, observed 188.0242.

6-(2-Benzo[1,3]dioxol-5-yl-aziridin-1-yl)-2,2-Dimethyl-3a,6a-dihydro-cyclopenta[1,3]dioxol-4-one(54). Triethylamine (0.4 mL, 3.0 mmol, 2.0 equiv) and 13-chloroenone 53(280 mg, 1.5 mmol, 1.0 equiv) were sequentially added to a stirredsolution of aziridine 15 (360 mg, 2.2 mmol, 1.5 equiv) intetrahydrofuran (10 mL) at 25° C. The resulting white mixture wasstirred at 25° C. for 3 h. The crude reaction mixture was loadeddirectly onto a column and purified by silica gel column chromatography(1% triethylamine and 49% benzene in ethyl acetate) to afford 54 (400mg, 85% yield) as a yellow foam. R_(f)=0.68 (1% triethylamine and 49%benzene in ethyl acetate); ¹H NMR (500 MHz, C₆D₆) δ 6.55-6.70 (m, 3H,ArH), 5.24-5.28 (m, 2H, OCH₂O), 5.14-5.18 (m, 1H, NCCH), 4.50-4.56 (m,1H, CH(OR)), 4.19-4.27 (m, 1H, CH(OR)), 2.46-3.18 (m, 1H, ArCHN),1.84-2.17 (m, 1H, CH₂N), 1.63-1.78 (m, 1H, CH₂N), 1.28-1.32 (m, 3H,CH₃), 1.10-1.12 (m, 3H, CH₃); IR (neat film) 2989 (w), 1703 (m), 1586(s) cm⁻¹; HRMS (ESI) m/z: Calcd for C₁₇H₁₈NO₅ (MH⁺) 316.1185, observed316.1186.

[3]Benzazepine 55. Cesium carbonate (3.2 g, 9.8 mmol, 4.0 equiv) wasadded to a stirred solution of aziridine 54 (770 mg, 2.4 mmol, 1.0equiv) in 1,4-dioxane (350 mL) at 25° C. The reaction vessel was sealedunder argon and heated to 100° C. via oil bath for 18 h. The reactionmixture was gravity filtered and concentrated by rotary evaporation. Theresidue was purified by passage through a plug of silica gel (ethylacetate) to afford 55 (590 mg, 76% yield) as a tan foam. R_(f)=0.27 (50%ethyl acetate in benzene); ¹H NMR (500 MHz, CDCl₃) δ 7.82 (br s, 1H,ArH), 6.54 (s, 1H, ArH), 5.93 (d, 1H, J=1.5 Hz, OCH₂O), 5.91 (d, 1H,J=1.5 Hz, OCH₂O), 5.77 (br s, 1H, NH), 4.97 (d, 1H, J=6 Hz, CH(OR)),4.65 (d, 1H, J=6 Hz, CH(OR)), 3.80-3.85 (m, 1H, ArCH₂CH₂N), 3.60-3.65(m, 1H, ArCH₂CH₂N), 2.95 (br t, 2H, J=4 Hz, ArCH₂CH₂N), 1.44 (s, 3H,CH₃), 1.43 (s, 3H, CH₃); ¹³C NMR (125 MHz, C₆D₆) δ 195.02, 165.26,146.76, 146.28, 133.02, 126.24, 113.71, 109.55, 109.10, 109.00, 100.84,78.98, 76.30, 47.65, 36.87, 27.89, 26.87; IR (neat film) 3266 (w), 2924(s), 2855 (m), 1705 (w), 1585 (s) cm⁻¹; HRMS (ESI) m/z: Calcd forC₁₇H₁₈NO₅ (MH⁺) 316.1185, observed 316.1189.

N-(trimethylsilyl)methyl vinylogous amide 59. Cesium carbonate (1.1 g,3.5 mmol, 2.0 equiv) and (iodomethyl)trimethylsilane (1.3 mL, 8.7 mmol,5.0 equiv) were sequentially added to a stirred solution of[3]benzazepine 55 (540 mg, 1.7 mmol, 1.0 equiv) in tetrahydrofuran (12mL) at 25° C. The resulting brown mixture was stirred at 25° C. for 20h. The reaction mixture was diluted with a saturated solution of sodiumsulfate (50 mL) and extracted with ethyl acetate (3×50 mL). The combinedorganic layers were dried (magnesium sulfate), gravity filtered, andconcentrated by rotary evaporation. The residue was purified by silicagel column chromatography (50% benzene in ethyl acetate) to afford 59(490 mg, 75% yield) as a pale yellow film. R_(f)=0.55 (50% benzene inethyl acetate); ¹H NMR (500 MHz, CDCl₃) δ 7.73 (s, 1H, ArH), 6.49 (s,1H, ArH), 5.92 (d, 1H, J=1.5 Hz, OCH₂O), 5.88 (d, 1H, J=1.5 Hz, OCH₂O),5.10 (d, 1H, J=6 Hz, CH(OR)), 4.66 (d, 1H, J=6 Hz, CH(OR)), 3.55-3.65(m, 2H, ArCH₂CH₂N), 3.20-3.40 (m, 2H, NCH₂SiMe₃), 2.85-3.00 (m, 2H,ArCH₂CH₂N), 1.44 (s, 3H, CH₃), 1.43 (s, 3H, CH₃), 0.14 (s, 9H,Si(CH₃)₃); ¹³C NMR (125 MHz, C₆D₆) δ 194.10, 164.04, 146.93, 146.24,133.16, 127.00, 113.48, 110.62, 109.77, 108.22, 100.95, 78.78, 75.94,57.48, 46.81, 35.82, 28.15, 26.84, −1.53; IR (neat film) 2924 (w), 1662(w), 1567 (s) cm⁻¹; HRMS (ESI) m/z; Calcd for C₂₁H₂₈NO₅Si (MH⁺)402.1737, observed 402.1745.

Hexacyclic sulfone 62. Pivaloyl chloride (62 μL, 0.50 mmol, 1.2 equiv)and silver trifluoromethanesulfonate (130 mg, 0.50 mmol, 1.2 equiv) weresequentially added to a stirred solution of vinylogous amide 59 (170 mg,0.42 mmol, 1.0 equiv) in dichloromethane (5.6 mL) at 25° C. Theresulting yellow mixture was stirred at 25° C. for 1 h, cooled to −45°C., and stirred for 15 min. Phenyl vinyl sulfone (280 mg, 1.7 mmol, 4.0equiv) and tetrabutylammonium triphenyldifluorosilicate (290 mg, 0.54mmol, 1.3 equiv) were sequentially added at −45° C. The resulting tanmixture was stirred at −45° C. for 4 h, warmed to 25° C., and stirredfor 16 h. The crude reaction mixture was loaded directly onto a columnand purified by silica gel column chromatography (50% hexane in ethylacetate) to afford 62 (190 mg, 77% yield) as a tan amorphous solid.R_(f)=0.43 (50% hexane in ethyl acetate); ¹H NMR (500 MHz, C₆D₆) δ 7.04(s, 1H, ArH), 6.80-6.85 (m, 3H, SO₂Ph), 6.70-6.75 (m, 2H, SO₂Ph), 6.45(s, 1H, ArH), 5.71 (d, 1H, J=5.5 Hz, CH(OR)), 5.32 (d, 1H, J=1.4 Hz,OCH₂O), 5.24 (d, 1H, J=1.4 Hz, OCH₂O), 4.20 (d, 1H, J=5.5 Hz, CH(OR)),3.80-3.85 (m, 1H, CH₂), 3.45-3.55 (m, 2H, CH₂), 3.20-3.35 (m, 2H, CH₂),2.55-2.60 (m, 2H, CH₂), 2.22-2.32 (m, 2H, CH₂), 1.28 (s, 3H, CH₃), 1.20(s, 3H, CH₃), 1.08 (s, 9H, C(CH₃)₃); ¹³C NMR (125 MHz, C₆D₆) δ 175.16,148.43, 148.00, 146.23, 140.11, 133.69, 133.10, 129.12, 128.43, 123.26,112.29, 110.61, 110.14, 101.18, 83.80, 80.59, 79.55, 63.46, 51.04,50.97, 38.89, 32.39, 32.27, 30.96, 28.16, 26.99, 26.97; IR (neat film)2981 (m), 2934 (m), 1751 (m), 1668 (w), 1568 (m) cm⁻¹; HRMS (ESI) m/z;Calcd for C₃₁H₃₆NO₈S (MH⁺) 582.2162, observed 582.2159.

Note: this numbering system is for the X-ray crystal structure of 62only and does not correspond to the numbering system of cephalotaxine(1).Crystal Data and Structure Refinement for 62:

Identification code ga61fas Empirical formula C68H84N2O16S2 Formulaweight 1249.49 Temperature 193(2) K Wavelength 0.71073 Å Crystal systemOrthorhombic Space group P 21 21 21 Unit cell dimensions a = 10.4431(16)Å a = 90°. b = 16.639(3) Å b = 90°. c = 38.548(6) Å g = 90°. Volume6698.2(18) Å³ Z 4 Density (calculated) 1.239 Mg/m³ Absorptioncoefficient 0.147 mm⁻¹ F(000) 2664 Crystal size 0.40 × 0.08 × 0.06 mm³Theta range for data collection 1.33 to 25.70°. Index ranges −12 <= h <=12, −20 <= k <= 20, −47 <= l <= 45 Reflections collected 32544Independent reflections 12606 [R(int) = 0.1206] Completeness to theta =25.70° 99.6% Absorption correction Integration Max. and min.transmission 0.9940 and 0.9617 Refinement method Full-matrixleast-squares on F² Data/restraints/parameters 12606/220/889Goodness-of-fit on F² 0.932 Final R indices [I > 2sigma(I)] R1 = 0.0655,wR2 = 0.1174 R indices (all data) R1 = 0.1715, wR2 = 0.1546 Absolutestructure parameter −0.03 (11) Largest diff. peak and hole 0.233 and−0.275 e · Å⁻³

Hexacyclic pyrrolidine 65. tert-Butyl alcohol (50 μL, 0.52 mmol, 10equiv) was added to hexacyclic sulfone 62 (14 mg, 24 μmol) at 25° C. Theresulting tan mixture was stirred at 25° C. for 10 min, cooled to −78°C., and stirred for 10 min. A 0.1 molar solution of samarium diiodide(2.6 mL, 0.26 mmol, 5.0 equiv) was added at −78° C. The resulting darkblue mixture was stirred at −78° C. for 10 min. Hexamethyl phosphorictriamide (0.22 mL, 1.3 mmol, 25 equiv) was added at −78° C. Theresulting purple mixture was stirred at −78° C. for 1 h, warmed to −45°C., and stirred for 2 h. The reaction mixture was warmed to 25° C.,diluted with water (60 mL), and extracted with ethyl acetate (4×50 mL).The combined organic layers were dried (magnesium sulfate), gravityfiltered, and concentrated by rotary evaporation. The residue waspurified by silica gel column chromatography (50% benzene in ethylacetate) to afford 65 (17 mg, 74% yield) as an off-white crystallinesolid. R_(f)=0.39 (50% benzene in ethyl acetate); ¹H NMR (500 MHz, C₆D₆)δ 7.03 (s, 1H, ArH), 6.45 (s, 1H, ArH), 5.72 (d, 1H, J=6 Hz, CH(OR)),5.31 (d, 1H, J=1.5 Hz, OCH₂O), 5.26 (d, 1H, J=1.5 Hz, OCH₂O), 4.56 (d,1H, J=6 Hz, CH(OR)), 3.70 (ddd, 1H, J=2, 12, 14 Hz, CH₂), 3.00 (ddd, 1H,J=3, 8, 11 Hz, CH₂), 2.82 (m, 1H, CH₂), 2.60-2.70 (m, 2H, CH₂), 2.50(ddd, 1H, J=1.4, 6.6, 12 Hz, CH₂), 2.24 (ddd, 1H, J=1.7, 4, 18 Hz, CH₂),1.78-1.88 (m, 1H, CH₂), 1.56-1.64 (m, 1H, CH₂), 1.51 (s, 3H, CH₃),1.40-1.48 (m, 1H, CH₂), 1.30 (s, 3H, CH₃), 1.10 (s, 9H, C(CH₃)₃); ¹³CNMR (125 MHz, C₆D₆) δ 175.43, 147.62, 147.18, 145.95, 132.86, 130.44,124.40, 111.97, 110.44, 110.25, 101.07, 86.00, 80.68, 78.90, 50.38,48.51, 38.88, 32.07, 30.75, 28.28, 27.04, 26.85, 25.10; IR (neat film)2930 (m), 1751 (m), 1485 (s) cm⁻¹; HRMS (ESI) m/z: Calcd forC₂₅H₃₂NO₆(MH⁺) 442.2230, observed 442.2231.

Hexacyclic enol 66. Schwartz's reagent (140 mg, 0.53 mmol, 3.0 equiv)was added to a stirred solution of enol-pivaloate 65 (78 mg, 0.18 μmol,1.0 equiv) in tetrahydrofuran (0.33 mL) at 25° C. The reaction vesselwas sealed under argon and heated to 40° C. via oil bath for 16 h. Thereaction mixture was diluted with water (10 mL) and extracted withdichloromethane (3×10 mL). The crude reaction mixture was loadeddirectly onto a column and purified by silica gel column chromatography(10% methanol in chloroform) to afford 66 (63 mg, 99% yield) as a tansolid. R_(f)=0.34 (10% methanol in chloroform); ¹H NMR (500 MHz, C₆D₆) δ6.44 (br s, 2H, ArH), 5.32 (d, 2H, J=1.5 Hz, OCH₂O), 5.29 (br s, 2H,C(O)CH), 4.77 (br s, 1H, OH), 2.00-2.50 (m, 10H, CH₂), 1.35 (s, 3H,CH₃), 1.34 (s, 3H, CH₃); IR (neat film) 3417 (w), 2986 (m), 2935 (m),2590 (w), 1720 (m), 1504 (m), 1485 (s) cm⁻¹; HRMS (ESI) m/z: Calcd forC₂₀H₂₄NO₅ (MH⁺) 358.1654, observed 358.1667.

Hexacyclic carbonate 67. Potassium bis(trimethylsilyl)amide (63 mg, 0.30mmol, 1.2 equiv) was added to a stirred solution of enol 66 (89 mg, 0.25mmol, 1.0 equiv) in tetrahydrofuran (2.5 mL) at 0° C. The resultingorange solution was stirred at 0° C. for 15 min. Benzyl chloroformate(43 μL, 0.30 mmol, 1.2 equiv) was added at 0° C. The resulting yellowsolution was stirred at 0° C. for 1 h. The reaction mixture was dilutedwith water (40 mL) and extracted with dichloromethane (2×40 mL). Thecombined organic layers were dried (magnesium sulfate), gravityfiltered, and concentrated by rotary evaporation. The residue waspurified by silica gel column chromatography (50% benzene in ethylacetate) to afford 67 (110 mg, 86% yield) as a tan foam. R_(f)=0.34 (10%methanol in chloroform); ¹H NMR (500 MHz, C₆D₆) δ 7.07 (s, 1H, ArH),6.94-6.97 (m, 3H, Ph), 6.90-6.93 (m, 2H, Ph), 6.41 (s, 1H, ArH), 5.77(d, 1H, J=6 Hz, C(O)CH), 5.24 (d, 1H, J=1.5 Hz, OCH₂O), 5.21 (d, 1H,J=1.5 Hz, OCH₂O), 4.76 (d, 1H, J=12 Hz, OCH₂Ph), 4.68 (d, 1H, J=12 Hz,OCH₂Ph), 4.56 (d, 1H, J=6 Hz, C(O)CH), 3.64 (m, 1H, CH₂), 2.98 (m, 1H,CH₂), 2.60-2.68 (m, 2H, CH₂), 2.46 (ddd, 1H, J=12, 6.5, 1.5 Hz, CH₂),2.28 (ddd, 1H, J=17, 4, 1.5 Hz, CH₂), 1.76-1.84 (m, 1H, CH₂), 1.54-1.60(m, 1H, CH₂), 1.48 (s, 3H, CH₃), 1.38-1.43 (m, 1H, CH₂), 1.30 (s, 3H,CH₃); ¹³C NMR (125 MHz, C₆D₆) δ 152.35, 147.79, 146.30, 146.12, 135.05,132.45, 130.82, 128.40, 128.25, 128.16, 123.69, 112.04, 110.12, 109.95,100.92, 85.70, 80.29, 78.70, 70.06, 50.21, 48.21, 31.85, 30.44, 28.10,26.70, 24.88; IR (neat film) 2932 (w), 1762 (m), 1504 (m), 1485 (m) 1379(m), 1222 (s) cm⁻¹; HRMS (ESI) m/z: Calcd for C₂₈H₃₀NO₇ (MH⁺) 492.2022,observed 492.2032.

Pentacyclic carbamate 68. Triethylamine (5.0 μL, 36 μmol, 4.0 equiv) andbenzyl chloroformate (5.0 μL, 36 μmol, 4.0 equiv) were sequentiallyadded to a stirred solution of enol 66 (3.2 mg, 9.0 μmol, 1.0 equiv) indichloromethane at 25° C. The resulting yellow solution was stirred at25° C. for 18 h. The crude reaction mixture was loaded directly onto acolumn and purified by silica gel column chromatography (40% benzene inethyl acetate) to afford 68 (2.2 mg, 50% yield) as a pale yellow film.R_(f)=0.76 (40% benzene in ethyl acetate); ¹H NMR (500 MHz, C₆D₆) δ 7.07(s, 1H, ArH), 6.94-6.98 (m, 3H, Ph), 6.90-6.94 (m, 2H, Ph), 6.41 (s, 1H,ArH), 5.77 (d, 1H, J=6 Hz, C(O)CH), 5.24 (d, 1H, J=1.5 Hz, OCH₂O), 5.21(d, 1H, J=1.5 Hz, OCH₂O), 4.75 (d, 1H, J=12 Hz, OCH₂Ph), 4.68 (d, 1H,J=12 Hz, OCH₂Ph), 4.57 (d, 1H, J=6 Hz, C(O)CH), 3.65 (m, 1H, CH₂), 2.99(m, 1H, CH₂), 2.82 (m, 1H, CH₂), 2.64 (m, 2H, CH₂), 2.47 (m, 1H, CH₂),2.27 (m, 1H, CH₂), 1.80 (m, 1H, CH₂), 1.48 (s, 3H, CH₃), 1.40 (m, 1H,CH₂), 1.30 (s, 3H, CH₃).

Pentacyclic diol S6. A 33% solution of methanol in 2 molar hydrochloricacid (5 mL) was added to acetonide 67 (60 mg, 0.12 mmol, 1.0 equiv) at25° C. The resulting cloudy white solution was stirred at 25° C. for 16h. The reaction mixture was diluted with methanol and concentrated byrotary evaporation. This process was repeated four times. The residuewas diluted with a 50% solution of methanol in toluene and concentratedby rotary evaporation. This process was repeated four times to afford S6(60 mg, 99% yield) as a white film. ¹H NMR (500 MHz, CD₃OD) δ 7.10-7.30(m, 5H, Ph), 6.73 (s, 1H, ArH), 6.70 (s, 1H, ArH), 5.92 (d, 1H, J=1 Hz,OCH₂O), 5.90 (d, 1H, J=1 Hz, OCH₂O), 5.10 (d, 1H, J=12 Hz, OCH₂Ph), 5.06(d, 1H, J=12 Hz, OCH₂Ph), 4.95 (d, 1H, J=6 Hz, CH(OH)), 4.40 (d, 1H, J=6Hz, CH(OH)), 3.64-3.74 (m, 2H, CH₂), 3.10-3.32 (m, 4H, CH₂), 2.45 (m,1H, CH₂), 2.00-2.10 (m, 2H, CH₂), 1.79 (m, 1H, CH₂); ¹³C NMR (125 MHz,CD₃OD) δ 152.46, 152.30, 150.03, 148.12, 136.05, 131.33, 129.77, 129.62,129.44, 126.73, 122.58, 111.40, 110.48, 103.02, 85.29, 73.97, 71.79,71.01, 53.31, 49.85, 30.55, 29.45, 23.00; IR (neat film) 3294 (s), 2957(m), 2605 (m), 1766 (s), 1672 (w), 1621 (w), 1504 (s), 1487 (s), 1458(s), 1380 (s), 1228 (s) cm⁻¹; HRMS (ESI) m/z: Calcd for C₂₅H₂₆NO₇(MH⁺)452.1709, observed 452.1717.

Pentacyclic mono-carbonate S7. Ytterbium trifluoromethanesulfonatehydrate (87 mg, 0.12 mmol, 1.0 equiv) and di-tert-butyldicarbonate (0.11mL, 0.48 mmol, 4.0 equiv) were sequentially added to a stirred solutionof pentacyclic diol S6 (58 mg, 0.12 mmol, 1.0 equiv) in dichloromethane(3.0 mL) at 0° C. The resulting cloudy pale yellow solution was stirredat 0° C. for 2 d. The reaction mixture was diluted with water (50 mL)and extracted with ethyl acetate (3×40 mL). The combined organic layerswere dried (magnesium sulfate), gravity filtered, and concentrated byrotary evaporation to afford crude S7 (70 mg) as a pale yellow foam.R_(f)=0.65 (10% methanol in chloroform); ¹H NMR (500 MHz, CD₃OD) δ7.30-7.35 (m, 3H, Ph), 7.26-7.30 (m, 2H, Ph), 6.65 (br s, 2H, ArH), 5.92(s, 2H, OCH₂O), 5.13 (br s, 2H, OCH₂Ph), 4.85 (d, 1H, J=6 Hz, CH(OH)),4.60 (d, 1H, J=6 Hz, CH(OBoc)), 3.42 (m, 1H, CH₂), 3.27 (m, 1H, CH₂),2.99 (ddd, 1H, J=14.5, 5, 2 Hz, CH₂), 2.90 (m, 1H, CH₂), 2.72-2.80 (m,2H, CH₂), 2.33 (dd, 1H, J=12.5, 7 Hz, CH₂), 1.60-1.80 (m, 4H, CH₂), 1.51(s, 9H, OC(CH₃)₃); IR (neat film) 3520 (br, w) 2981 (m), 2933 (m), 1809(m), 1743 (s), 1505 (m), 1487 (s), 1456 (m), 1372 (s), 1283 (s), 1225(s) cm⁻¹; HRMS (ESI) m/z: Calcd for C₃₀H₃₄NO₉ (MH⁺) 552.2234, observed552.2216.

Pentacyclic α-oxyketone 69. ortho-Iodoxy benzoic acid (100 mg, 0.36mmol, 3.0 equiv) was added to a stirred solution of crude mono-carbonateS7 (66 mg, 0.12 mmol, 1.0 equiv) in dimethylsulfoxide (3.0 mL) at 25° C.The resulting orange solution was stirred at 25° C. for 20 h. Thereaction mixture was diluted with water (200 mL) and extracted withdiethyl ether (5×40 mL). The combined organic layers were dried(magnesium sulfate), gravity filtered, and concentrated by rotaryevaporation. The residue was purified by silica gel columnchromatography (12.5% ethyl acetate in benzene) to afford 69 (33 mg, 50%yield from 67) as a pale yellow film. R_(f)=0.45 (12.5% ethyl acetate inbenzene); ¹H NMR (500 MHz, C₆D₆) δ 6.95-6.99 (m, 5H, Ph), 6.71 (s, 1H,ArH), 6.29 (s, 1H, ArH), 5.79 (s, 1H, CH(OBoc)), 5.17 (d, 1H, J=1.5 Hz,OCH₂O), 5.13 (d, 1H, J=1.5 Hz, OCH₂O), 4.81 (d, 1H, J=12 Hz, OCH₂Ph),4.73 (d, 1H, J=12 Hz, OCH₂Ph), 3.09 (ddd, 1H, J=14.5, 11.5, 4.5 Hz,CH₂), 2.67 (ddd, 1H, J=17, 11, 6 Hz, CH₂), 2.60 (ddd, 1H, J=14.5, 8, 2Hz, CH₂), 2.45-2.55 (m, 2H, CH₂), 2.36 (m, 1H, CH₂), 2.15 (dd, 1H, J=13,7 Hz, CH₂), 1.86 (m, 1H, CH₂), 1.46 (m, 1H, CH₂), 1.32 (s, 9H, OC(CH₃)₃)1.30 (m, 1H, CH₂); ¹³C NMR (125 MHz, C₆D₆) δ 191.35, 158.90, 153.68,152.04, 149.30, 146.46, 142.65, 134.88, 132.69, 128.64, 128.58, 128.56,121.72, 110.44, 110.07, 101.37, 82.49, 81.78, 73.31, 71.00, 48.45,41.84, 34.29, 32.79, 27.62, 24.78; IR (neat film) 2978 (m), 2929 (m),1753 (s), 1736 (s), 1692 (m), 1505 (m), 1485 (s) cm⁻¹; HRMS (ESI) m/z:Calcd for C₃₀H₃₂NO₉ (MH⁺) 550.2077, observed 550.2080.

Pentacyclic enone S8. A stirred solution of α-oxyketone 69 (30 mg, 55μmol, 1.0 equiv) in acetone (2.0 mL) was subjected to fivefreeze-pump-thaw cycles. A solution of water (1.0 mL) was subjected to 5freeze-pump-thaw cycles, chromium(II) chloride (67 mg, 0.55 mmol, 10equiv) was added, and the resulting blue/green solution was subjected toanother five freeze-pump-thaw cycles. The aqueous chromium solution wastransferred via cannula to the reaction mixture at 25° C. The resultinggreen solution was subjected to another 5 freeze-pump-thaw cycles. Thegreen solution was stirred at 25° C. for 1 h. The reaction mixture wasdiluted with water (50 mL) and extracted with ethyl acetate (4×40 mL).The combined organic layers were dried (magnesium sulfate), gravityfiltered, and concentrated by rotary evaporation. The residue waspurified by silica gel column chromatography (50% benzene in ethylacetate) to afford S8 (10 mg, 42% yield) as a colorless film. R_(f)=0.45(12.5% ethyl acetate in benzene); ¹H NMR (500 MHz, C₆D₆) δ 6.96-7.02 (m,5H, Ph), 6.83 (s, 1H, ArH), 6.37 (s, 1H, ArH), 5.21 (d, 1H, J=1.5 Hz,OCH₂O), 5.16 (d, 1H, J=1.5 Hz, OCH₂O), 4.88 (d, 1H, J=12 Hz, OCH₂Ph),4.77 (d, 1H, J=12 Hz, OCH₂Ph), 3.14 (ddd, 1H, J=15.5, 12, 4 Hz, CH₂),2.80 (ddd, 1H, J=16.5, 11.5, 5.5 Hz, CH₂), 2.54-2.62 (m, 2H, C(O)CH₂,CH₂), 2.47-2.53 (m, 2H, CH₂), 2.37-2.45 (m, 2H, C(O)CH₂, CH₂), 1.55 (m,1H, CH₂), 1.43 (m, 1H, CH₂), 1.23-1.29 (m, 2H, CH₂); ¹³C NMR (125 MHz,C₆D₆) δ 196.81, 161.39, 152.63, 149.13, 146.48, 145.12, 134.96, 132.54,128.46, 128.31, 128.25, 122.90, 110.29, 109.39, 101.17, 70.58, 70.17,51.35, 48.80, 42.97, 38.83, 32.44, 24.37; IR (neat film) 2924 (m), 1767(s), 1718 (s), 1643 (w), 1504 (m), 1485 (s), 1382 (m), 1227 (s) cm⁻¹;HRMS (ESI) m/z: Calcd for C₂₅H₂₄NO₆ (MH⁺) 434.1604, observed 434.1616.

(+)-Demethylcephalotaxinone (70). 10% Palladium on carbon (5 mg, ˜33 wt.%) was added to a stirred solution of benzyl carbonate S8 (14 mg, 32μmol, 1.0 equiv) in ethyl acetate (5.0 mL) at 25° C. The resulting blackmixture was charged with an atmosphere of hydrogen (balloon) and stirredat 25° C. for 6 h. The crude reaction mixture was eluted through a shortplug of celite (ethyl acetate followed by dichloromethane) and theorganic layer was concentrated by rotary evaporation to afford (+)-70(10 mg, 99% yield) as a colorless film. R_(f)=0.30 (10% methanol inchloroform); ¹H NMR (500 MHz, C₆D₆) δ 7.04 (s, 1H, ArH), 6.42 (s, 1H,ArH), 5.27 (d, 1H, J=1.5 Hz, OCH₂O), 5.23 (d, 1H, J=1.5 Hz, OCH₂O),2.83-2.97 (m, 2H, CH₂), 2.52-2.62 (m, 3H, CH₂), 2.43 (d, 1H, J=18 Hz,C(O)CH₂), 2.30-2.36 (m, 2H, C(O)CH₂, CH₂), 1.58 (m, 1H, CH₂), 1.48 (m,1H, CH₂), 1.35 (m, 1H, CH₂), 1.19 (dd, 1H, J=12, 6 Hz, CH₂); ¹³C NMR(125 MHz, C₆D₆) δ 218.26, 161.31, 148.42, 148.02, 146.26, 132.65,124.69, 110.51, 110.12, 101.18, 70.67, 51.28, 49.22, 44.37, 39.15,32.75, 24.54; IR (neat film) 3386 (w, br) 2922 (m), 1702 (s), 1506 (m),1484 (s) cm⁻¹; HRMS (ESI) m/z: Calcd for C₁₇H₁₈NO₄ (MH⁺) 300.1236,observed 300.1246; [α]²³ _(D) 358.8 (c 0.39, CHCl₃).

(−)-Cephalotaxinone (S9). Trimethyl orthoformate (33 μL, 0.30 mmol, 10equiv) and tosylic acid monohydrate (12 mg, 60 μmol, 2.0 equiv) weresequentially added to a stirred solution of (+)-demethylcephalotaxinone(70) (9.0 mg, 30 μmol, 1.0 equiv) in dichloromethane (0.65 mL) at 0° C.The resulting dark orange solution was stirred at 0° C. for 30 min,warmed to 25° C., and stirred for 6.5 h. The reaction mixture wasdiluted with a saturated solution of sodium bicarbonate (30 mL) andextracted with dichloromethane (4×20 mL). The combined organic layerswere dried (sodium sulfate), gravity filtered, and concentrated byrotary evaporation. The residue was purified by silica gel columnchromatography (10% methanol in chloroform) to afford (−)-S9 (5.5 mg,55% yield) as a pale yellow film. R_(f)=0.46 (10% methanol inchloroform); ¹H NMR (500 MHz, C₆D₆) δ 6.58 (s, 1H, ArH), 6.47 (s, 1H,ArH), 5.76 (s, 1H, vinyl H), 5.34 (d, 1H, J=1.5 Hz, OCH₂O), 5.32 (d, 1H,J=1.5 Hz, OCH₂O), 3.16 (s, 3H, OCH₃), 2.71 (m, 1H, CH₂), 2.44-2.60 (m,2H, CH₂), 2.28-2.40 (m, 2H, CH₂), 2.01 (dd, 1H, J=14, 7 Hz, CH₂), 1.72(m, 1H, CH₂), 1.30-1.50 (m, 4H, CH₂); IR (neat film) 2928 (m), 1722 (s),1624 (m), 1503 (m), 1486 (s), 1229 (s) cm⁻¹; HRMS (ESI) m/z: Calcd forC₁₈H₂₀NO₄ (MH⁺) 314.1392, observed 314.1390.

(−)-Cephalotaxine (1). Sodium borohydride (27 mg, 0.70 mmol, 40 equiv)was added to a stirred solution of (−)-cephalotaxinone (S9) (5.5 mg, 18μmol, 1.0 equiv) in methanol (0.65 mL) at −78° C. The resulting whitemixture was stirred at −78° C. for 10 min, warmed to 25° C., and stirredfor 1 h. The reaction mixture was diluted with water (30 mL) andextracted with dichloromethane (4×15 mL). The combined organic layerswere dried (sodium sulfate), gravity filtered, and concentrated byrotary evaporation to afford (−)-1 (5.2 mg, 95% yield) as a pale yellowfilm. R_(f)=0.08 (10% methanol in chloroform); ¹H NMR (500 MHz, CDCl₃) δ6.68 (s, 1H, ArH), 6.65 (s, 1H, ArH), 5.90 (s, 2H, OCH₂O), 4.93 (s, 1H,vinyl H), 4.76 (d, 1H, J=9 Hz, CH(OH)), 3.73 (s, 3H, OCH₃), 3.68 (d, 1H,J=9 Hz, ArCHCH(OH)), 3.35 (m, 1H, CH₂), 3.08 (m, 1H, CH₂), 2.92 (ddd,1H, J=12, 11, 7 Hz, CH₂), 2.54-2.62 (m, 2H, CH₂), 2.36 (dd, 1H, J=14, 7Hz, CH₂), 2.00 (m, 1H, CH₂), 1.60-1.90 (m, 4H, CH₂); IR (neat film) 3411(br, w), 2926 (m), 1651 (m), 1503 (m), 1486 (s), 1222 (s) cm⁻¹; HRMS(ESI) m/z: Calcd for C₁₈H₂₂NO₄ (MH⁺) 316.1549, observed 316.1559.

[2-tert-Butyl-4-(3-methyl-but-2-enyl)-5-oxo-[1,3]dioxolan-4-yl]-aceticacid (74). A solution of LHMDS (413 mg, 2.47 mmol, 1.00 equiv) in THF (5mL) at −78° C. was transferred via cannula to a stirred solution of acid72 (500 mg, 2.47 mmol, 1.00 equiv) in THF (25 mL) at −78° C. Theresulting solution was stirred at −78° C. for 15 minutes. A solution ofLHMDS (496 mg, 2.96 mmol, 1.20 equiv) in THF (5 mL) at −78° C. was thenadded via cannula and the resulting solution was stirred for 20 min at−78° C. 3,3 dimethylallyl bromide (316 μL, 2.72 mmol, 1.10 equiv) wasthen added via syringe and the resulting solution was stirred at −78° C.for 19 h, at which time the reaction was quenched with 25 mL sat'dNH₄Cl, removed from the cold bath, and allowed to warm to RT. Thesolution was then poured into 75 mL 1N HCl, extracted with 3×75 mLCH₂Cl₂, the combined organic phases were dried over MgSO₄ andconcentrated via rotary evaporation to yield an oily solid. Purificationby silica gel column chromatography (19:1 MeOH:CH₂Cl₂) yielded 74 (438mg, 66%) as a white powder. R_(f)=0.51 (19:1 CH₂Cl₂:MeOH); ¹H NMR (400MHz, CDCl₃) δ 5.16 (m, 2H, CH(CH₃)₃; vinyl H), 2.83 (m, 2H, CH₂), 2.50(d, 2H, J=7.7 Hz, CH₂), 1.74 (d, 3H, J=0.8 Hz, CH₃), 1.64 (d, 3H, J=0.8Hz, CH₃), 0.93 (s, 9H, CH(CH₃)₃; ¹³C NMR (100 mhz, CDCl₃) δ 174.91,173.84, 137.96, 115.55, 108.42, 80.54, 39.44, 34.28, 32.40, 25.97,23.60, 18.03; IR (neat film) 2973 (m), 2916 (m), 1800 (s), 1710 (s),1181 (m), 1156 (m) cm⁻¹; HRMS (ESI) m/z calcd for C₁₄H₂₃O₅ (M⁺)271.1545, observed 271.1553; [α]_(D)=−266° (c 2.98 CHCl₃).

2-Hydroxy-2-(3-methyl-but-2-enyl)-succinic acid 1-benzyl ester (75). Asolution of dioxolanone 74 (120 mg, 0.444 mmol, 1.00 equiv) in THF (4.5mL) was cooled to 0° C. and benzyl alcohol (69 μL, 0.67 mmol, 1.5 equiv)was added via syringe followed by a 60% dispersion of NaH in mineral oil(45 mg, 1.1 mmol, 2.5 equiv) which resulted in vigorous evolution ofgas. The solution was allowed to stir at 0° C. for 30 min, at which timethe reaction was quenched with 4.5 mL NaHCO₃, removed from the cold bathand allowed to warm to room temperature. The solution was then pouredinto H₂O (4.5 mL), washed with CH₂Cl₂ 6 mL), acidified to pH<5 with 1NHCl, and then extracted with Et₂O (4×6 mL). The combined ethereal phaseswere dried over MgSO₄ and solvent removal by rotary evaporation yieldeda white solid which was purified by silica gel column chromatography(70:28:2 hex:EtOAc:HOAc) to yield 75 (114 mg, 88%) as a white solid.R_(f)=0.39 (60:38:2 EtOAc:Hex:HOAc); ¹H NMR (500 MHz, CDCl₃) δ 7.35 (m,5H, ArH), 5.20 (s, 2H, PhCH₂), 5.07 (m, 1H, vinyl H), 3.00 (d, 1H,J=16.7 Hz, C(O)CH₂), 2.76 (d, 1H, J=16.7 Hz, C(O)CH₂), 2.41 (m, 2H,CHCH₂), 1.67 (d, 3H, J=0.7 Hz, CH₃), 1.54 (d, 3H, J=0.7 Hz, CH₃); ¹³CNMR (100 MHz, CDCl₃) δ 176.43, 174.60, 136.79, 135.21, 128.71, 128.64,128.61, 116.45, 75.41, 67.95, 42.69, 38.14, 26.06, 18.09; IR (neat film)3483 (br m), 2968 (m), 1736 (s), 1498 (w), 1195 (s) cm⁻¹; HRMS (ESI) m/zcalcd for C₁₆H₂₀O₅Na (M⁺+Na⁺) 315.1208, observed 315.1214; [α]_(D)=−18°(c 2.98, CHCl₃).

2-(3-Methyl-but-2-enyl)-4-oxo-oxetane-2-carboxylic acid benzyl ester(S10). A solution of hydroxyester 75 (100 mg, 0.342 mmol, 1.00 equiv)and triethylamine (166 μL, 1.20 mmol, 3.50 equiv) in CH₂Cl₂ (14 mL) wasadded via syringe pump over 4 h to a solution of 2,4,6-trichlorobenzoylchloride (80 μL, 0.51 mmol, 1.5 equiv) and N,N-dimethylaminopyridine(DMAP) (46 mg, 0.38 mmol, 1.1 equiv) in CH₂Cl₂ (3.4 mL). The solutionwas then allowed to stir for 1 h after complete addition after whichtime it was quenched with H₂O (10 mL). The phases were separated and theaqueous phase was extracted with CH₂Cl₂ (2×10 mL). The organic phaseswere combined, dried over Na₂SO₄, and the solvent was removed via rotaryevaporation to yield a red solid which was purified by silica gel columnchromatography (CH₂Cl₂) to yield S10 (47 mg, 50%) as a pale yellow oil.R_(f)=0.79 (60:38:2 Hex:EtOAc:HOAc); ¹H NMR (500 MHz, CDCl₃) δ 7.37 (m,5H, ArH), 5.25 (s, 2H, ArCH₂), 5.09 (m, 1H, vinyl H), 3.61 (d, 1H,J=16.4 Hz, C(O)CH₂), 3.36 (d, 1H, J=16.4 Hz, C(O)CH₂), 2.79 (m, 2H,CHCH₂), 1.70 (d, 3H, J=0.8 Hz, CH₃), 1.60 (d, 3H, J=0.8 Hz, CH₃); ¹³CNMR (100 MHz, CDCl₃) δ 169.21, 165.84, 138.67, 134.67, 128.68, 128.38,114.24, 76.28, 67.84, 45.56, 33.43, 25.87, 17.99; IR (neat film) 2966(m), 2914 (m), 1842 (s), 1737 (s), 1452 (m) 962 (m) cm⁻¹; HRMS (EI) m/zcalcd for C₁₆H₁₈O₄ (M⁺) 274.120509, observed 274.120646; [α]_(D)=+1.2°(c 2.92, CHCl₃).

2-(3-Methyl-butyl)-4-oxo-oxetane-2-carboxylic acid (76). To a solutionof benzyl ester S10 (220 mg, 0.802 mmol, 1.00 equiv) in EtOAc (8 mL) wasadded Pd/C (10 wt % on C, 44 mg, 20% by weight). The resultingsuspension was stirred under H₂ (1 atm) for 23 h, then filtered througha plug of celite. Solvent removal by rotary evaporation yielded an oilwhich showed alkene peaks by 1H NMR, so the residue was resubjected tothe reaction conditions to yield carboxylic acid 76 (150 mg, >99%) as aclear, colorless oil. R_(f)=0.11 (60:38:2 hex:EtOAc:HOAc); ¹H NMR (400MHz, CDCl₃) δ 10.30 (br s, 1H, C(O)OH), 3.71 (d, 1H, J=16.6 Hz,C(O)CH₂), 3.45 (d, 1H, J=16.6 Hz, C(O)CH₂), 2.19 (ddd, 1H, J=14.2, 12.3,4.8 Hz, CCH₂), 2.04 (ddd, 1H, J=14.2, 12.3, 4.8 Hz, CCH₂), 1.61 (septet,1H, J=6.6 Hz (CH₃)₂CH), 1.40 (m, 1H, (CH₃)₂CHCH₂), 1.27 (m, 1H,(CH₃)₂CHCH₂), 0.92 (d, 6H, J=6.6 Hz (CH₃)₂); ¹³C NMR (400 MHz, CDCl₃) δ174.96, 165.69, 76.43, 46.78, 33.17, 32.109, 27.89, 22.27, 22.20; IR(neat film) 3514 (br m), 3184 (br s), 2958 (s), 1828 (s), 1729 (s), 1408(m), 1173 (s) cm⁻¹; [α]_(D)=22.1° (c 1.67, CHCl₃).

Deoxyharringtonine, β-lactone (I-3a). To a solution of β-lactone 76 (8.9mg, 0.048 mmol, 1.5 equiv) and triethylamine (19.9 μL, 0.143 mmol, 4.50equiv) in CH₂Cl₂ (320 μL) was added 2,4,6-trichlorobenzoyl chloride (8.2μL, 0.052 mmol, 1.7 equiv) via syringe. The resulting dark purplesolution was stirred at 23° C. for 1 h. This solution was thentransferred via syringe to a solution of cephalotaxine (1) (10 mg, 0.032mmol, 1.0 equiv) and N,N-dimethylaminopyridine (DMAP) in CH₂Cl₂ (320μL). This solution was then stirred for 15 min, concentrated under astream of N₂, and loaded directly onto a silica gel column that had beenpacked with 5% triethylamine in hexanes. The column was eluted with 1:1hex:EtOAc to yield I-3a (12.4 mg, 81%) as an oil. R_(f)=0.39 (1:1hex:EtOAc on plates pretreated with 5% TEA in pentane); ¹H NMR (500 MHz,CDCl₃) δ 6.60 (app d, 2H, ArH), 5.91 (dd, 1H, J=9.6, 0.7 Hz, ArCHCH),5.86 (dd, 2H, J=4.1, 1.4 Hz, OCH₂O), 5.08 (s, 1H, vinyl H), 3.81 (d, 1H,J=9.5 Hz, ArCHCH), 3.69 (s, 3H, OCH₃), 3.10 (m, 2H, CH₂), 2.98 (d, 1H,J=16.5 Hz, C(O)CH₂), 2.93 (m, 1H, CH₂), 2.73 (d, 1H, J=16.5 Hz,C(O)CH₂), 2.58 (m, 2H, CH₂), 2.35 (dd, 1H, J=14.3, 6.9, CH₂), 2.04 (m,1H, CH₂), 1.88 (m, 2H, CH₂), 1.75 (m, 2H, CH₂), 1.62 (m, 1H, CH₂), 1.47(septet, 1H, J=6.7 Hz, (CH₃)₂CH), 1.15 (m, 1H, CH₂), 1.02 (m, 1H, CH₂),0.85 (dd, 6H, J=6.7, 1.2 Hz, (CH₃)₂CH); ¹³C (500 MHz, CDCl₃) δ 171.03,168.57, 166.25, 113.17, 109.96, 109.91, 101.11, 76.53, 75.62, 65.63,57.36, 54.05, 48.60, 46.31, 41.74, 33.21, 31.97, 27.91, 22.46, 22.14,20.39; IR (neat film) 2958 (m), 1842 (s), 1750 (s), 1656 (m), 1504 (m),1488 (s), 1037 (m) cm⁻¹; HRMS (EI) m/z calcd for C₂₇H₃₃NO₇ (M+)483.225703 found 483.224659; [α]_(D)=−95° (c 2.77, CHCl₃).

Deoxyharringtonine (2). To a solution of β-lactone I-3a (18 mg, 0.0372mmol, 1.00 equiv) in MeOH (370 μL) was added a freshly prepared solutionof 0.5M NaOMe in MeOH (82 μL, 0.0409 mmol, 1.10 equiv). After 15 min thesolution was quenched with half sat'd NH₄Cl solution (300 μL) andpartitioned between H₂O (10 mL) and CH₂Cl₂ (10 mL). The phases wereseparated and the aqueous phase was extracted with CH₂Cl₂ (2×10 mL), thecombined organic phases were dried over MgSO₄, and concentrated byrotary evaporation to yield a yellow oil that was purified by silica gelcolumn chromatography (70:28:2 benzene:hex:TEA) to yielddeoxyharringtonine (2) (14.6 mg, 76%) as a clear, colorless oil.R_(f)=0.24 (9:1 benzene:EtOAc on plates pretreated with 5% TEA inpentane); ¹H NMR (500 MHz, CDCl₃) δ 6.62 (s, 1H, ArH), 6.53 (s, 1H,ArH), 5.99 (dd, 1H, J=9.8, 0.7 Hz ArCHCH), 5.86 (dd, 2H, J=11.8, 1.5 Hz,OCH₂O), 5.04 (d, 1H, J=0.6 Hz, vinyl H), 3.77 (d, 1H, J=9.8 Hz, ArCHCH),3.67 (s, 3H, OCH₃), 3.57 (s, 3H, OCH₃), 3.48 (s, 1H, OH), 3.12 (m, 2H,CH₂), 2.94 (td, 1H, J=11.1, 7.1 Hz, CH₂), 2.58 (m, 2H, CH₂), 2.37 (dd,1H, J=14.3, 7 Hz, CH₂), 2.27 (d, 1H, J=16.6 Hz, C(O)CH₂), 2.04 (m, 1H,CH₂), 1.91 (m, 1H, CH₂), 1.88 (d, 1H, J=16.2 Hz, C(O)CH₂), 1.75 (m, 2H,CH₂), 1.42 (m, 3H, CH₂ & (CH₃)₂CH), 1.29 (m, 1H, CH₂), 0.97 (m, 1H,CH₂), 0.84 (d, 3H, J=7.0 Hz, (CH₃)₂CH), 0.83 (d, 3H, J=7.0 Hz, (CH₃)₂CH)¹³C NMR (400 MHz, CDCl₃) δ 174.19, 170.57, 157.87, 146.75, 145.92,133.43, 128.55, 128.46 (residual benzene), 112.75, 109.80, 100.94,100.16, 74.83, 74.69, 70.70, 57.25, 55.98, 54.12, 51.63, 48.82, 43.54,42.89, 36.87, 31.70, 31.48, 28.13, 22.83, 22.38, 20.42; IR (neat film)3527 (w), 2955 (m), 1748 (s), 1653 (m), 1504 (m), 1488 (s), 1225 (s),1036 (m), 754 (m); HRMS (ESI) calcd for C₂₈H₃₈NO₈ (M⁺+H) 516.2597observed 516.2581; [α]_(D)=−110° (c 1.46, CHCl₃).

Lit ¹H NMR of 2 (100 MHz, CDCl₃) δ 6.59 (s, 1H, ArH), 6.50 (s, 1H, ArH),5.96 (d, 1H, J=10 Hz ArCHCH), 5.82 (m, 2H, OCH₂O), 5.01 (s, 1H, vinylH), 3.64 (s, 3H, OCH₃), 3.53 (s, 3H, OCH₃), 2.06 (q, 2H, J=16 Hz, CH₂),0.82 (d, J=6 Hz, (CH₃)₂CH); [α]_(D)=−119° (c 0.6, CHCl₃) (Mikolajczak,K. L.; Powell, R. G.; Smith, C. R. Jr. Tetrahedron, 1972, 28, 1995).

Also, T. Ross Kelly and K. L. Mikolajczak compare deoxyharringtoninewith its C2′-sidechain epimer: ¹H NMR of C2′-epi-2 Deoxyharringtonine: δ6.59 (s, 1H, ArH), 6.50 (s, 1H, ArH), 5.97 (d, 1H, ArCHCH), 3.64 (s, 3H,CH₃), 3.53 (s, 3H, CH₃), 2.26 (d, 1H, CH₂), 1.86 (d, 1H, CH₂) Sidechainepimer: 6.56 (s, 2H, ArH), 5.86 (d, 1H, ArCHCH), 3.62 (s, 3H, CH₃) 3.60(s, 3H, CH₃), 2.66 (d, 1H, CH₂), 2.46 (d, 1H, CH₂) The spectrum of oursynthetic 1 clearly matches that of deoxyharringtonine and not itsC2′-sidechain epimer (Mikolajczak, K. L.; Smith, C. R. Jr.; Weisleder,D.; Kelly, T. R.; McKenna, J. C.; Christenson, P. A. Tet. Lett, 1974,283-286).

(R)-1-benzyl 4-methyl 2-hydroxy-2-(3-methylbut-2-enyl)succinate (77). Toa solution of acid 75 (175.2 mg, 0.599 mmol, 1.00 equiv) in 7:2 PhH:MeOH(6.0 mL) was added a 2.0 M solution of TMSCHN₂ (449 μL, 0.899 mmol, 1.50equiv.). After the resulting gas evolution had subsided, the solvent wasremoved by rotary evaporation to yield methyl ester 77 (183.7 mg, 100%)as a clear, colorless oil. R_(f)=0.55 (2:1 hex:EtOAc); ¹H NMR (500 MHz,CDCl₃) δ 7.36 (m, 5H, aryl H), 5.23 (d, 1H, J=12.1 Hz, PhCH₂), 5.19 (d,1H, J=12.1 Hz, PhCH₂), 5.08 (m, 1H, vinyl H), 3.68 (s, 1H, OH), 3.62 (s,3H, OCH₃), 2.95 (d, 1H, J=16.2 Hz, C(O)CH₂), 2.72 (d, 1H, J=16.3 Hz,C(O)CH₂), 2.41 (m, 2H, CHCH₂), 1.67 (s, 3H, C(CH₃)₂), 1.54 (s, 3H,C(CH₃)₂); ¹³C NMR (125 MHz, CDCl₃) δ 174.84, 171.43, 136.54, 135.46,128.70, 128.66, 128.60, 116.75, 75.65, 67.79, 51.93, 42.81, 38.11,26.06, 18.09; IR (neat film) 3514 (m), 3034 (w), 2955 (m), 1742 (s),1498 (w), 1439 (s), 753 (m), 699 (m) cm⁻¹; LRMS (ESI) calc'd forC₁₇H₂₂O₅Na (M+Na⁺) 329.2, found 329.1.

(R)-1-benzyl 4-methyl 2-acetoxy-2-(3-methylbut-2-enyl)succinate (S11).To a solution of tertiary alcohol 77 (33.0 mg, 0.109 mmol, 1.00 equiv)in dry pyridine (500 μL) at 0° C. was added acetic anhydride (114 μL,1.09 mmol, 10.0 equiv) and N,N-dimethylaminopyridine (DMAP) (3.0 mg,0.0246 mmol, 0.23 equiv). The solution was then stirred at 23° C. for 17h at which time further DMAP (13.0 mg, 1.09 mmol, 1.00 equiv) and aceticanhydride (22 μL, 0.21 mmol, 1.9 equiv) were added. After 1 h thesolution was diluted with H₂O (10 mL) and extracted with CH₂Cl₂ (3×10mL). The combined organic extracts were washed with 0.1M aqueous CuSO₄soln, dried over MgSO₄, and concentrated by rotary evaporation to yielda dark red oil. Purification by silica gel column chromatography (5:1hexanes:EtOAc) provided S11 (28.1 mg, 74%) as a colorless oil.R_(f)=0.32 (5:1 hexanes:EtOAc); ¹H NMR (500 MHz, CDCl₃) δ 7.35 (m, 5H,ArH), 5.14 (m, 2H, ArCH₂), 5.00 (tt, 1H, J=7.5, 1.3 Hz, vinyl H), 3.64(s, 3H, CO₂CH₃), 3.27 (d, 1H, J=14.7 Hz, C(O)CH₂), 2.96 (d, 1H, J=14.7Hz, C(O)CH₂), 2.80 (dd, 1H, J=14.6, 7.6 Hz, CHCH₂), 2.69 (dd, 1H,J=14.6, 7.6 Hz, CHCH₂), 2.06 (s, 3H, C(O)CH₃), 1.67 (s, 3H, CCH₃), 1.56(s, 3H, CCH₃); ¹³C NMR (125 MHz, CDCl₃) δ 170.34, 170.10, 169.79,137.21, 135.45, 128.64, 128.50, 128.46, 115.89, 80.51, 67.48, 51.85,37.41, 34.35, 26.11, 21.09, 18.00; IR (neat film) 3067 (w), 2955 (w),1746 (s), 1441 (m), 1371 (m), 1227 (m); LRMS (ESI) calcd for C₁₉H₂₄O₆Na(M⁺+Na) 371.16 observed 371.00.

(R)-2-acetoxy-2-(2-methoxy-2-oxoethyl)-5-methylhex-4-enoic acid (78). Toa solution of benzyl ester S11 (28.0 mg, 0.0804 mmol, 1.00 equiv) inEtOAc (1.5 mL) was added 10% Pd/C (3.5 mg, 13 wt %). The resultingsuspension was stirred under H₂ (1 atm) for 15 h and filtered through aplug of celite. Solvent removal by rotary evaporation yielded 78 (20.9mg, 100%) as a clear, colorless oil. ¹H NMR (500 MHz, CDCl₃) δ10.34 (brs, 1H, CO₂H), 3.68 (s, 3H, CO₂CH₃), 3.29 (d, 1H, J=14.8 Hz, C(O)CH₂),3.00 (d, 1H, J=14.8 Hz, C(O)CH₂), 2.09 (s, 3H, C(O)CH₃), 2.02 (m, 2H,CCH₂), 1.54 (septet, 1H, J=6.6 Hz, CH), 1.22 (m, 2H, CHCH₂), 0.89 (d,6H, J=6.6 Hz, (CH₃)₂CH); ¹³C NMR (125 MHz, CDCl₃) δ 175.83, 170.18,169.84, 80.49, 52.02, 37.55, 33.54, 31.89, 28.11, 22.55, 22.39, 21.08;IR (neat film) 3182 (v br m), 2958 (m), 2873 (m), 1746 (s), 1440 (m),1370 (m), 1209 (s), 645 (w); LRMS (ESI) calcd for C₁₂H₂₀O₆Na (M⁺+Na)283.13 observed 283.01.

(R)-benzyl2-(2-methoxy-2-oxoethyl)-5,5-dimethyltetrahydrofuran-2-carboxylate(S12). To a solution of alcohol 77 (183.6 mg, 0.599 mmol, 1.00 equiv) in1:1 THF:H₂O (9.2 mL) was added Hg(OAc)₂ (382 mg, 1.199 mmol, 2.00equiv). The resulting solution was stirred at 23° C. for 45 minutes. A0.5M solution of NaBH₄ in 3M NaOH (1.2 mL, 0.599 mmol, 1.00 equiv) wasthen added by syringe, resulting in an immediate precipitation of Hg⁰.After stirring for 5 minutes, the suspension was partitioned between 20mL sat'd NH₄Cl soln. and 20 mL EtOAc. The phases were separated and theaqueous phase was extracted with 2×20 mL EtOAc. The combined organicphases were dried over MgSO₄ and solvent removal yielded a greysuspension that was purified by silica gel column chromatography (5:1hex:EtOAc) to yield tetrahydrofuran S12 (141.6 mg, 77%) as a clear,colorless oil. R_(f)=0.58 (2:1 hex:EtOAc); ¹H NMR (500 MHz, CDCl₃) δ7.34 (m, 5H, aryl H), 5.21 (d, 1H, J=12.3 Hz, PhCH₂), 5.17 (d, 1H,J=12.3 Hz, PhCH₂), 3.59 (s, 3H, OCH₃), 2.91 (d, 1H, J=15.4 Hz, C(O)CH₂),2.81 (d, 1H, J=15.4 Hz, C(O)CH₂), 2.41 (m, 1H, CH₂), 2.16 (m, 1H, CH₂),1.85 (m, 1H, CH₂), 1.78 (m, 1H, CH₂), 1.30 (s, 3H, C(CH₃)₂), 1.24 (s,3H, (CCH₃)₂); ¹³C NMR (125 MHz, CDCl₃) δ 173.70, 170.54, 135.93, 128.59,128.43, 128.32, 84.26, 83.96, 67.10, 51.80, 43.93, 37.88, 35.58, 29.09,28.33; IR (neat film) 3036 (w), 2973 (m), 1743 (s), 1500 (w), 1458 (m),1440 (m), 701 (m) cm⁻¹; LRMS (ESI) calc'd for C₁₇H₂₂O₅Na (M+Na⁺) 329.2,found 329.1.

(R)-2-(2-methoxy-2-oxoethyl)-5,5-dimethyltetrahydrofuran-2-carboxylicacid (80). To a solution of benzyl ester S12 (141.6 mg, 0.462 mmol, 1.00equiv) in EtOAc (4.6 mL) was added 14.2 mg 10% Pd/C. The atmosphere inthe vessel was replaced with H₂ under balloon pressure and the reactionwas stirred at 23° C. for 2 hours, at which time it was filtered througha plug of celite and flushed with EtOAc. Solvent removal by rotaryevaporation provided acid 80 (99.1 mg, 99%) as a white solid. R_(f)=0.07(2:1 hex:EtOAc); ¹H NMR (500 MHz, CDCl₃) δ 3.69 (s, 3H, OCH₃), 3.13 (d,1H, J=15.9 Hz, C(O)CH₂), 2.67 (d, 1H, J=15.9 Hz, C(O)CH₂), 2.43 (m, 1H,CH₂), 2.22 (m, 1H, CH₂), 1.87 (m, 2H, CH₂), 1.39 (s, 3H, C(CH₃)₂), 1.31(s, 3H, C(CH₃)₂); ¹³C NMR (125 MHz, CDCl₃) δ 175.72, 170.03, 85.91,84.23, 52.08, 43.66, 37.67, 36.16, 28.69, 28.55; IR (neat film)˜3100-2800 (br m), 2983 (s), 1753 (s), 1733 (s), 1459 (w), 1370 (w),1265 (s), 1192 (m), 1106 (m), 778 (w) cm⁻¹; LRMS (ESI) calc'd forC₁₀H₁₆O₅Na (M+Na⁺) 239.1, found 239.0.

Anhydroharringtonine (5). To a solution of acid 80 (13.7 mg, 0.0634mmol, 2.00 equiv) and triethylamine (29.1 μL, 0.209 mmol, 6.6 equiv) inCH₂Cl₂ (320 μL) was added 2,4,6-trichlorobenzoyl chloride (10.9 μL,0.0697 mmol, 2.20 equiv) via syringe. The resulting colorless solutionwas stirred at 23° C. for 1 h, then transferred via syringe to asolution of cephalotaxine (1) (10.0 mg, 0.0317 mmol, 1.00 equiv) andN,N-dimethylaminopyridine (DMAP) (4.4 mg, 0.0360 mmol, 1.14 equiv) inCH₂Cl₂ (320 μL). This solution was then stirred for 1 hour, then loadeddirectly onto a silica gel column. The column was eluted with 2% TEA in9:1 toluene:EtOAc to yield 5 (16.1 mg, 99%) as a white solid. R_(f)=0.31(2% TEA in 9:1 toluene:EtOAc on plates pretreated with 5% TEA inpentane); ¹H NMR (500 MHz, CDCl₃) δ 6.58 (s, 1H, aryl H), 6.56 (s, 1H,aryl H), 5.87 (m, 3H, OCH₂O, arylCHCH), 5.02 (s, 1H, vinyl H), 3.80 (d,1H, J=9.8 Hz, arylCHCH), 3.68 (s, 3H, OCH₃), 3.58 (s, 3H, OCH₃),3.18-3.06 (m, 2H, CH₂), 2.93 (m, 1H, CH₂), 2.58 (m, 2H, CH₂), 2.33 (m,1H, CH₂), 2.32 (d, 1H, J=15.1 Hz, C(O)CH₂), 2.26 (d, 1H, J=15.2 Hz,C(O)CH₂), 2.03 (m, 2H, CH₂), 1.87 (m, 2H, CH₂), 1.75 (m, 2H, CH₂), 1.65(m, 2H, CH₂), 1.24 (s, 3H, C(CH₃)₂), 1.14 (s, 3H, C(CH₃)₂); ¹³C NMR (125MHz, CDCl₃) δ 172.97, 170.33, 158.04, 146.81, 145.88, 133.37, 128.66,113.23, 109.74, 100.89, 99.86, 84.03, 83.80, 74.61, 70.73, 57.33, 56.49,54.14, 51.62, 48.95, 43.61, 42.63, 37.68, 34.92, 31.78, 28.96, 28.22,20.49; IR (neat film) 2965 (m), 2880 (m), 2796 (w), 1740 (s), 1654 (s),1503 (m), 1487 (s), 1223 (s), 1036 (s) cm⁻¹; LRMS (ESI) calc'd forC₂₈H₃₆NO₈ (M+Na+) 514.2, found 514.2; [α]_(D)=−144° (c 1.08, CHCl₃).

2-((2R,4R)-4-allyl-2-tert-butyl-5-oxo-1,3-dioxolan-4-yl) acetic acid(S13). A solution of LHMDS (413 mg, 2.47 mmol, 1.00 equiv) in THF (5 mL)at −78° C. was transferred via cannula to a stirred solution of acident-72 (500 mg, 2.47 mmol, 1.00 equiv) in THF (25 mL) at −78° C. Theresulting solution was stirred at −78° C. for 10 minutes. A solution ofLHMDS (621 mg, 3.71 mmol, 1.50 equiv) in THF (7 mL) at −78° C. was thenadded via cannula and the resulting solution was stirred for 20 min at−78° C. allyl bromide (439 μL, 5.19 mmol, 2.10 equiv) was then added viasyringe and the resulting solution was stirred at −78° C. for 21 h, atwhich time the reaction was partitioned between 75 mL 1 N HCl and 75 mLCH₂Cl₂, the phases were separated and the aqueous phase was extractedwith 2×50 mL CH₂Cl₂. The combined organic phases were dried over MgSO₄and concentrated via rotary evaporation to yield an oily solid.Purification by silica gel column chromatography (19:1 MeOH:CH₂Cl₂)yielded S13 (344 mg, 59%) as a clear, colorless oil. R_(f)=0.69 (60:38:2EtOAc:Hex:HOAc); ¹H NMR (500 MHz, CDCl₃) δ 5.77 (m, 1H, vinyl H), 5.22(m, 3H, vinyl H; CH(CH₃)₃), 2.86 (d, 1H, J=16 Hz, CH₂), 2.81 (d, 1H,J=16.0 Hz, CH₂), 2.55 (m, 2H, CH₂), 0.92 (s, 9H, CH(CH₃)₃); ¹³C NMR (125MHz, CDCl₃) δ 174.96, 173.49, 130.11, 121.34, 108.47, 79.90, 39.62,38.18, 34.45, 23.66; IR (neat film) ˜3500-2500 (br s), 2966 (s), 1793(s), 1718 (s), 1165 (m) cm⁻¹; LRMS (ESI) calcd. for C₁₂H₁₈O₅Na (M+Na⁺)265.1, observed 264.9.

(R)-3-(benzyloxycarbonyl)-3-hydroxyhex-5-enoic acid (81). A solution ofdioxolanone S13 (1.10 g, 4.54 mmol, 1.00 equiv) in THF (45 mL) wascooled to 0° C. and benzyl alcohol (564 μL, 5.45 mmol, 1.20 equiv) wasadded via syringe followed by a 60% dispersion of NaH in mineral oil(454 mg, 11.35 mmol, 2.50 equiv) which resulted in vigorous evolution ofgas. The solution was allowed to warm to 23° C. over 90 min, at whichtime the reaction was again cooled to 0° C., quenched with 45 mL 1 NHCl, poured into 45 mL EtOAc. The phases were separated and the aqueousphase was extracted with a further 3×45 mL EtOAc. The combined organicphases were dried over MgSO₄ and solvent removal by rotary evaporationyielded an oil which was purified by silica gel column chromatography(60:40:2 hex:EtOAc:HOAc) to yield 81 (1.02 g, 85%) as a clear, colorlessoil. R_(f)=0.60 (38:60:2 hex:EtOAc:HOAc); ¹H NMR (500 MHz, CDCl₃) δ 7.37(m, 5H, aryl H), 5.74 (m, 1H, vinyl H), 5.22 (d, 1H, J=10.1 Hz, PhCH₂),5.18 (d, 1H, J=10.1 Hz, PhCH₂), 5.11 (d, 1H, J=8.8 Hz, vinyl H), 5.06(d, 1H, J=17.1 Hz, vinyl H), 2.99 (d, 1H, J=16.6 Hz, C(O)CH₂), 2.76 (d,1H, J=16.6 Hz, C(O)CH₂), 2.45 (d, 2H, J=7.2, CHCH₂); ¹³C NMR (125 MHz,CDCl₃) δ 176.19, 174.34, 135.14, 131.13, 128.74, 128.68, 120.01, 74.98,68.08, 43.83, 42.74; IR (neat film) ˜3500-2500 (br m), 3077, 1737 (s),1641 (w), 1219 (m) cm⁻¹; LRMS (ESI) calcd. for C₁₄H₁₆O₅Na (M+Na⁺) 287.1,observed 286.9.

(R)-benzyl 2-allyl-4-oxooxetane-2-carboxylate (82). A solution ofhydroxyacid 81 (1.02 g, 3.86 mmol, 1.00 equiv) and triethylamine (519μL, 17.37 mmol, 4.50 equiv) in CH₂Cl₂ (77 mL) was added via syringe pumpover 4 h to a solution of 2,4,6-trichlorobenzoyl chloride (904 μL, 5.79mmol, 1.50 equiv) and N,N-dimethylaminopyridine (DMAP) (519 mg, 4.25mmol, 1.10 equiv) in CH₂Cl₂ (39 mL). The solution was then allowed tostir for 30 minutes after complete addition after which it was quenchedwith H₂O (100 mL). The phases were separated and the aqueous phase wasextracted with CH₂Cl₂ (2×100 mL). The organic phases were combined,dried over MgSO₄, and the solvent was removed via rotary evaporation toyield a black oil which was purified by silica gel column chromatography(CH₂Cl₂) to yield 82 (639 mg, 67%) as a yellow oil. R_(f)=0.52 (CH₂Cl₂);¹H NMR (500 MHz, CDCl₃) δ 7.38 (m, 5H, aryl H), 5.76 (m, 1H, vinyl H),5.26 (s, 2H, PhCH₂), 5.22 (m, 2H, vinyl H), 3.65 (d, 1H, J=16.5 Hz,C(O)CH₂), 3.42 (d, 1H, J=16.5 Hz, C(O)CH₂), 2.89 (dd, 1H, J=14.6, 6.8Hz, CHCH₂), 2.80 (dd, 1H, J=14.6, 6.8 Hz, CHCH₂); ¹³C NMR (125 MHz,CDCl₃) δ 169.03, 165.61, 134.75, 129.10, 128.95, 128.89, 128.59, 121.82,75.65, 68.17, 45.86, 39.06; IR (neat film) 3034 (w), 1843 (s), 1741 (s),1644 (w), 1456 (m) cm⁻¹; LRMS (ESI) calcd. for C₁₄H₁₄O₄Na (M+Na⁺) 269.1,observed 269.1.

(R,E)-benzyl2-(4-(benzyloxy)-4-methylpent-2-enyl)-4-oxooxetane-2-carboxylate (85). Asolution of alkene 82 (58.8 mg, 0.239 mmol, 1.00 equiv) in benzyl ether83 (842 mg, 4.78 mmol, 20 equiv) was subjected to two freeze-pump-thawcycles. Grubbs catalyst, 2^(nd) generation (20.1 mg, 0.0237 mmol, 0.10equiv) was then added and the resulting solution was subjected to onemore freeze-pump-thaw cycle then allowed to stir at 23° C. for 16 h.Another portion of catalyst (10.3 mg, 0.0121 mmol, 0.051 equiv) was thenadded and the solution was again subjected to one freeze-pump-thaw cycleand allowed to stir at 23° C. for 8 h. A third portion of catalyst (10.2mg, 0.0120 mmol, 0.050 equiv) was added and the solution was subjectedto one freeze-pump-thaw cycle then allowed to stir at 23° C. for 25 h.The crude reaction mixture was then loaded directly onto a pH 7.0buffered silica gel (10 wt % buffer) column which was eluted with agradient eluant (1:1 hex:CH₂Cl₂ to CH₂Cl₂) to yield 85 (57.6 mg, 61%) asa yellow oil and 84 (11.5 mg 22%) as a yellow oil. Data for dimer 85:R_(f)=0.28 (CH₂Cl₂); ¹H NMR (500 MHz, CDCl₃) δ 7.4-7.2 (m, 10H, aryl H),5.76 (d, 1H, J=15.9 Hz, (CH₃)₂CH), 5.57 (dt, 2H, J=15.8, 7.2 Hz, CH₂CH),5.22 (s, 2H, CO₂CH₂), 4.31 (s, 2H, COHCH₂), 3.64 (d, 1H, J=16.4 Hz,C(O)CH₂), 3.37 (d, 1H, J=16.5 Hz, C(O)CH₂), 2.90 (dd, 1H, J=14.6, 7.0Hz, CCH₂), 2.80 (dd, J=14.5, 7.3 Hz, CCH₂), 1.31 (d, 6H, J=2.8 Hz,C(CH₃)₂); ¹³C NMR (125 MHz, CDCl₃) δ 168.98, 165.50, 143.38, 139.56,134.72, 128.97, 128.93, 128.56, 128.45, 127.41, 127.35, 120.22, 75.82,75.30, 68.14, 65.11, 46.01, 37.90, 26.49, 26.41; IR (neat film) 3032(m), 2976 (m), 1838 (s), 1743 (s), 1498 (m), 1455 (m), 1059 cm⁻¹; HRMS(ESI) calcd. for C₂₄H₂₆O₅Na (M+Na⁺) 417.1678, found 417.1673.

Data for dimer 84: ¹H NMR (400 MHz, CDCl₃) δ 7.37 (m, 10H, aryl H), 5.54(m, 2H, vinyl H), 5.24 (s, 4H, PhCH₂), 3.60 (d, 2H, J=16.5 Hz, C(O)CH₂),3.32 (d, 2H, J=16.5 Hz, C(O)CH₂), 2.8 (m, 4H, CCH₂); ¹³C NMR (125 MHz,CDCl₃) δ 168.75, 165.28, 134.73, 128.98, 128.90, 128.67, 128.62, 127.87,75.44, 68.22, 46.15, 38.05.

Recycling of Dimer 84. A solution of dimer 84 (36.5 mg, 0.0786 mmol,1.00 equiv) in benzyl ether 83 (576 mg, 3.27 mmol, 41.6 equiv) wassubjected to 2× freeze-pump-thaw cycles. Grubbs catalyst, 2^(nd)generation (6.9 mg, 0.00818 mmol, 0.10 equiv) was added and theresulting solution was subjected to one more freeze-pump-thaw cycle thenallowed to stir at 23° C. for 14 h. Another portion of catalyst (7.1 mg,0.00836, 0.11 equiv) was added and the solution was subjected to onefreeze-pump-thaw cycle then allowed to stir at 23° C. for 9.5 h. A thirdportion of catalyst (6.8 mg, 0.0080 mmol, 0.10 equiv) was added and thesolution was subjected to one freeze-pump-thaw cycle then allowed tostir at 23° C. for 18.5 h. The crude reaction mixture was loadeddirectly onto a pH 7.0 buffered silica gel (10 wt % buffer) column whichwas eluted with a gradient eluant (1:1 hex:CH₂Cl₂ to CH₂Cl₂) to yield 85(40.2 mg, 65%) as a colorless oil. Data are identical to that reportedabove.

(R,E)-2-(4-(benzyloxy)-4-methylpent-2-enyl)-4-oxooxetane-2-carboxylicacid (86). To a solution of benzyl ester 85 (52.8 mg, 0.134 mmol, 1.00equiv.) were added TEA (3.0 μL, 0.0214 mmol, 0.16 equiv.),triethylsilane (32.1 μL, 0.201 mmol, 1.50 equiv.), and Pd(OAc)₂ (1.6 mg,0.0071 mmol, 0.053 equiv.). The resulting black solution was stirred at23° C. for 1 h then partitioned between 10 mL sat'd NH₄Cl solution and10 mL CH₂Cl₂. The phases were separated and the aqueous phase wasextracted with 2×10 mL CH₂Cl₂. The combined aqueous phases were driedover MgSO₄ and solvent removal by rotary evaporation left a brown oilthat upon purification by silica gel column chromatography (4% HOAc in1:1 hex:EtOAc) yielded acid 86 (34.4 mg, 85%) as a clear, colorless oil.R_(f)=0.17 (4% HOAc in 1:1 hex:EtOAc); ¹H NMR (500 MHz, CDCl₃) δ 10.09(br s, 1H, CO₂H), 7.33-7.23 (m, 5H, aryl H), 5.81 (d, 1H, J=15.9 Hz,(CH₃)₂CCH), 5.62 (m, 1H, CH₂CH), 4.35 (s, 2H, PhCH₂), 3.57 (d, 1H,J=16.6 Hz, C(O)CH₂), 3.36 (d, 1H, J=16.6, Hz, C(O)CH₂), 2.87 (dd, 1H,J=14.6, 7.1 Hz), 2.74 (dd, 1H, J=14.7, 7.3 Hz), 1.35 (s, 6H, (CH₃)₂);¹³C NMR (125 MHz, CDCl₃) δ 173.48, 165.44, 143.27, 139.13, 128.48,127.66, 127.53, 120.34, 75.85, 65.24, 46.06, 37.57, 26.51, 26.29; IR(neat film) ˜3500-2500 (br m), 3031 (w), 2977 (m), 1843 (s), 1745 (s),1497 (w), 1453 (w), 1149 (m) cm⁻¹; LRMS (ESI) calc'd for C₁₇H₂₀O₅Na327.1, found 326.9.

(R,E)-2-(4-(benzyloxy)-4-methylpent-2-enyl)-4-oxooxetane-2-cephalotaxylcarboxylate S14. To a solution of β-lactone 86 (34.5 mg, 0.114 mmol,2.00 equiv) and triethylamine (52.4 μL, 0.378 mmol, 6.6 equiv) in CH₂Cl₂(570 μL) was added 2,4,6-trichlorobenzoyl chloride (19.6 μL, 0.126 mmol,2.20 equiv) via syringe. The resulting dark purple solution was stirredat 23° C. for 1 h, then transferred via syringe to a solution ofcephalotaxine (1) (18.0 mg, 0.0571 mmol, 1.00 equiv) andN,N-dimethylaminopyridine (DMAP) (7.8 mg, 0.063 mmol, 1.10 equiv) inCH₂Cl₂ (570 μL). This solution was then stirred for 25 minutes thenloaded directly onto a pH 7.0 buffered silica gel column. The column waseluted with 1% TEA in 9:1 toluene:EtOAc to yield S14 (33.3 mg, 97%) as alight yellow oil. R_(f)=0.24 (1% TEA in 9:1 toluene:EtOAc on a TLC platepretreated with 5% TEA in pentane); ¹H NMR (500 MHz, CDCl₃) δ 7.32-7.22(m, 5H, Aryl H), 6.60 (s, 1H, aryl H), 6.59 (s, 1H, aryl H), 5.86 (m,3H, O(CH₂)O, arylCHCH), 5.71 (d, 1H, J=15.9 Hz, (CH₃)₂CCH), 5.47 (dt,1H, J=15.8, 8.5 Hz, CH₂CH), 5.08 (s, 1H, CHCOCH₃), 4.31 (s, 2H PhCH₂),3.80 (d, 1H, J=9.5 Hz, ArCHCH), 3.68 (s, 3H, OCH₃), 3.08 (m, 2H CH₂),2.98 (d, 1H, J=16.4 Hz, C(O)CH₂), 2.94 (m, 1H, CH₂), 2.64 (d, 1H, J=16.5Hz, C(O)CH₂), 2.59 (m, 3H, CH₂), 2.43-2.34 (m, 2H, CH₂), 2.02 (m, 1H,CH₂), 1.90 (m, 1H, CH₂), 1.75 (m, 2H, CH₂), 1.32 (s, 6H, C(CH₃)₂); ¹³CNMR (125 MHz, CDCl₃) δ 168.22, 165.58, 156.71, 147.19, 146.13, 143.19,139.81, 133.73, 128.49, 128.01, 127.52, 127.37, 120.57, 113.50, 109.98,101.39, 101.24, 75.95, 75.67, 75.41, 70.87, 65.17, 57.50, 56.66, 54.20,48.74, 45.39, 43.72, 37.73, 31.70, 26.55, 26.39, 20.60; IR (neat film)2972 (m), 2801 (w), 1842 (s), 1751 (s), 1654 (s), 1504 (s), 1223 (s)cm⁻¹; LRMS (ESI) calc'd for C₃₅H₄₀NO₈ 602.3, found 602.5; [α]_(D)=−88°(c 3.3, CHCl₃).

(R,E)-1-cephalotaxyl 4-methyl2-(4-(benzyloxy)-4-methylpent-2-enyl)-2-hydroxysuccinate I-5. To asolution of β-lactone S14 (33.0 mg, 0.0548 mmol, 1.00 equiv) in MeOH(550 μL) was added a freshly prepared solution of 0.5M NaOMe in MeOH(121 μL, 0.0603 mmol, 1.10 equiv). After 10 min the solution wasquenched with sat'd NH₄Cl solution (300 μL) and partitioned betweensat'd NH₄Cl solution (10 mL) and CH₂Cl₂ (10 mL). The phases wereseparated and the aqueous phase was extracted with CH₂Cl₂ (2×10 mL), thecombined organic phases were dried over MgSO₄, and concentrated byrotary evaporation to yield a yellow oil that was purified by silica gelcolumn chromatography (1% TEA in 9:1 toluene:EtOAc) to yield 1-5 (27.5mg, 79%) as a clear, colorless oil. R_(f)=0.18 (9:1 toluene:EtOAc onplates pretreated with 5% TEA in pentane); ¹H NMR (500 MHz, CDCl₃) δ7.33-7.22 (m, 5H, aryl H), 6.61 (s, 1H, aryl H), 6.55 (s, 1H, aryl H),5.94 (d, 1H, J=9.7 Hz, arylCHCH), 5.85 (app d, 2H, OCH₂O), 5.62 (d, 1H,(CH₃)₂CCH), 5.51 (m, 1H, CH₂CH), 5.05 (s, 1H, CHCOCH₃), 4.33 (s, 2H,PhCH₂), 3.77 (d, 1H, J=9.8 Hz, arylCHCH), 3.66 (s, 3H, OCH₃), 3.58 (s,3H, OCH₃), 3.45 (s, 1H, OH), 3.12 (m, 2H, CH₂), 3.94 (m, 1H, CH₂), 2.59(m, 2H, CH₂), 2.38 (dd, 1H, J=14.1, 6.9 Hz, CH₂), 2.29 (d, 1H, J=16.4Hz), C(O)CH₂), 2.20 (m, 2H, CH₂), 2.01 (m, 1H, CH₂), 1.96 (d, 1H, J=16.4Hz, C(O)CH₂), 1.90 (m, 1H, CH₂), 1.75 (m, 2H, CH₂), 1.33 (d, 6H, J=3.1,(CH₃)₂C); ¹³C NMR (125 MHz, CDCl₃) δ 173.72, 170.50, 146.98, 146.07,141.16, 140.02, 128.44, 127.66, 127.29, 123.16, 113.06, 109.86, 101.05,100.50, 75.47, 75.25, 74.61, 65.15, 57.49, 56.16, 54.15, 51.80, 48.81,43.56, 41.92, 41.77, 31.63, 26.69, 26.52, 20.50; IR (neat film) 3527(m), 2971 (s), 1749 (s), 1654 (s), 1504 (s), 1487 (s), 1363 (s), 1039(s), 932 (m), 736 (s); LRMS (ESI) calcd for C₃₆H₄₄NO₉ (M⁺+H) 634.29found 634.08; [α]_(D)=−110° (c 1.5, CHCl₃).

Homoharringtonine (3). To a solution of allylic benzyl ether I-5 (12.6mg, 0.0199 mmol, 1.00 equiv.) in MeOH (200 μL) was added 10% Pd/C (2.4mg, 20% by wt). The atmosphere in the vessel was replaced with H₂ underballoon pressure and the suspension was stirred at 23° C. until LRMS(ESI) showed complete reduction of the alkene (26 h). Glacial aceticacid (20 μL) was added via syringe and the solution was stirred under H₂at 23° C. for 21 h. Further 10% Pd/C (1.3 mg) and glacial acetic acid(20 μL) were added and the suspension was stirred under H₂ for 24 h thenfiltered through a plug of celite. The solvent was removed by rotaryevaporation and the resulting film was purified by silica gel columnchromatography (2% TEA in 1:1 toluene:EtOAc) to yield homoharringtonine(3) (8.5 mg, 79%) as a colorless film. Rf=0.25 (2% TEA in 1:1toluene:EtOAc on TLC plates pretreated with 5% TEA in pentane); ¹H NMR(500 MHz, CDCl₃) δ 6.62 (s, 1H, aryl H), 6.54 (s, 1H, aryl H), 6.00 (d,1H, J=9.8 Hz, arylCHCH), 5.87 (app dd, 2H, J=2.9, 1.4, OCH₂O), 5.05 (s,1H, CHCOCH₃), 3.77 (d, 1H, J=9.7 Hz, arylCHCH), 3.67 (s, 3H, OCH₃), 3.57(s, 3H, OCH₃), 3.52 (s, 1H, OH), 3.10 (m, 2H, CH₂), 3.00 (m, 1H, CH₂),2.60 (m, 2H, CH₂), 2.40 (dd, 1H, J=14.2, 6.9 CH₂), 2.26 (d, 1H, J=16.5Hz, C(O)CH₂), 2.02 (m, 1H, CH₂), 1.90 (d, 1H, J=16.5 Hz, C(O)CH₂), 1.89(m, 1H, CH₂), 1.75 (m, 2H, CH₂), 1.45-1.36 (m, 5H, CH₂), 1.27 (br s, 1H,CH₂), 1.19 (app d, 6H, (CH₃)₂C); ¹³C NMR (125 MHz, CDCl₃) δ 173.62,170.38, 157.63, 146.86, 145.96, 141.06, 139.93, 133.44, 128.43, 128.33,127.55, 127.18, 123.06, 112.95, 109.75, 100.94, 100.43, 75.37, 75.16,74.51, 70.66, 65.05, 57.38, 56.11, 54.06, 51.69, 48.73, 43.50, 41.82,41.67, 31.56, 26.59, 26.43, 20.42; IR (neat film) 3526 (br m), 2960 (s),1744 (s), 1654 (s), 1503 (s), 1487 (s), 1366 (s), 1225 (s), 932 (m), 754(s) cm⁻¹; LRMS (ESI) calcd for C₂₉H₄₀NO₉ (M⁺+H) 545.26 found 545.7;[α]_(D)=−112° (c 0.75, CHCl₃).

Homodeoxyharringtonine (4). To a solution of allylic benzyl ether I-5(12.2 mg, 0.0192 mmol, 1.0 equiv) in glacial acetic acid (800 μL) wasadded degussa grade (E101 NE/W from Aldrich) Pd/C (10 wt % dry basis,50% water, 25.3 mg, 62 mol %). The atmosphere in the vessel was replacedwith H₂ (1 atm) and the suspension was stirred for 20 h at 23° C.,filtered through a plug of celite, flushed with glacial acetic acid, andthe solvent was removed by azeotrope with toluene. The crude product waspurified by pH 7.0 buffered (10 wt %) silica gel column chromatography(2% TEA in 1:1 toluene:EtOAc) to yield homodeoxyharringtonine (4) (7.0mg, 69%) as a colorless film as well as homoharringtonine (2.8 mg 27%)as a colorless film. Rf=0.66 (2% TEA in 1:1 toluene:EtOAc on TLC platespretreated with 5% TEA in pentane); ¹H NMR (500 MHz, CDCl₃) δ 6.62 (s,1H, aryl H), 6.53 (s, 1H, aryl H), 5.99 (d, 1H, J=9.8 Hz, arylCHCH),5.86 (dd, 2H, J=9.8, 1.5 Hz OCH₂O), 5.04 (s, 1H, CHCOCH₃), 3.77 (d, 1H,J=9.8 Hz, arylCHCH), 3.66 (s, 3H, OCH₃), 3.57 (s, 3H, OCH₃), 3.48 (s,1H, OH), 3.11 (m, 2H, CH₂), 2.95 (m, 1H, CH₂), 2.59 (m, 2H, CH₂), 2.38(dd, J=14.8, 6.9, 1H, CH₂), 2.31 (d, 1H, J=16.5 Hz, C(O)CH₂), 2.05 (m,1H, CH₂), 1.91 (m, 1H, CH₂), 1.90 (d, 1H, J=16.5 Hz, C(O)CH₂), 1.75 (m,2H, CH₂), 1.49 (m, 1H, CH₂), 1.38 (m, 3H, CH₂), 1.09 (m, 3H, CH₂), 0.85(app t, 6H, J=6.4 Hz, CH(CH₃)₂); ¹³C NMR (125 MHz, CDCl₃) δ 174.24,170.61, 157.95, 146.82, 145.96, 133.48, 128.55, 112.81, 109.84, 100.96,100.20, 74.84, 74.80, 70.75, 57.38, 56.00, 54.09, 51.63, 48.75, 43.53,42.79, 39.16, 39.08, 31.49, 27.93, 22.81, 22.51, 20.71, 20.44; IR (neatfilm) 3529 (br w), 2953 (s), 1748 (s), 1654 (m), 1504 (m), 1487 (s),1224 (s), 932 (m) cm⁻¹; LRMS (ESI) calcd for C₂₉H₄₀NO₈ (M⁺+H) 530.27found 530.3; [α]_(D)=−112° (c 0.7, CHCl₃).

(R)-4-oxo-2-propyloxetane-2-carboxylic acid (S15). To a solution ofbenzyl ester 82 (30.3 mg, 0.123 mmol, 1.0 equiv) in EtOAc (1.5 mL) wasadded 10% Pd/C (3.2 mg, 0.0030 mmol, 2.4 mol %). The atmosphere in thevessel was replaced with H₂ under balloon pressure and the mixture wasstirred at 23° C. for 15 h. The suspension was then filtered through aplug of celite and flushed with EtOAc (25 mL). Solvent removal yieldedcarboxylic acid S15 (19.0 mg, 97%) as a yellow oil. ¹H NMR (500 MHz,CDCl₃) δ 11.3 (br s, 1H, CO₂H), 3.73 (d, 1H, J=16.6 Hz, C(O)CH₂), 3.45(d, 1H, J=16.5 Hz, C(O)CH₂), 2.20-2.15 (m, 1H, CCH₂), 2.06-2.00 (m, 1H,CCH₂), 1.57-1.50 (m, 1H, CCH₂CH₂), 1.48-1.44 (m, 1H, CCH₂CH₂), 1.01 (t,3H, J=7.3 Hz, CH₃); ¹³C NMR (125 MHz, CDCl₃) δ 175.04, 165.78, 76.44,47.07, 37.38, 17.20, 13.93; IR (neat film) 3500-3000 (br m), 2966 (m),2878 (m), 1834 (s), 1736 (s), 1410 (w), 1143 (m), 960 (w) cm⁻¹.

Beta-lactone I-1. To a solution of acid S15 (9.9 mg, 0.063 mmol, 2.0equiv) and cephalotaxine (1) (9.9 mg, 0.031 mmol, 1.0 equiv) in CH₂Cl₂(630 μL) were added triethylamine (29 μL, 0.21 mmol, 6.6 equiv) and2,4,6-trichlorobenzoyl chloride (10.9 μL, 0.0697 mmol, 2.20 equiv) viasyringe and N,N-dimethylaminopyridine (DMAP) (4.4 mg, 0.0360 mmol, 1.14equiv) as a solid. The resulting dark purple solution was stirred at 23°C. for 15 m (TLC showed complete consumption of cephalotaxine after 5m), then loaded directly onto a silica gel column. The column was elutedwith 2% TEA in 9:1 toluene:EtOAc to yield I-1 (11.7 mg, 81%) as acolorless oil. R_(f)=0.48 (2% TEA in 9:1 toluene:EtOAc on platespretreated with 5% TEA in pentane); ¹H NMR (500 MHz, CDCl₃) δ 6.61 (s,1H, aryl H), 6.59 (s, 1H, aryl H), 5.90 (d, 1H, J=9.5 Hz, ArCHCH), 5.86(dd, 2H, J=7.8, 1.5 Hz (OCH₂O), 5.08 (s, 1H, vinyl H), 3.81 (d, 1H,J=9.6 Hz, ArCHCH), 3.69 (s, 3H, OCH₃), 3.14-3.07 (m, 2H, CH₂), 3.02 (d,1H, J=16.5 Hz, ArCHCH), 2.96-2.90 (m, 1H, CH₂), 2.85 (d, 1H, J=16.5 Hz,ArCHCH), 2.61-2.56 (m, 2H, CH₂), 2.36 (dd, 1H, J=14.3, 6.9 Hz, CH₂),2.05-2.00 (m, 1H, CH₂), 1.92-1.88 (m, 1H, CH₂), 1.84-1.72 (m, 3H, CH₂),1.64-1.58 (m, 1H, CH₂), 1.20-1.07 (m, 2H, CH₂), 0.86 (t, 3H, J=14.8 Hz,CH₂CH₃); ¹³C NMR (125 MHz, CDCl₃) δ 168.62, 166.26, 156.79, 147.07,145.99, 133.86, 127.89, 113.16, 110.02, 101.10, 76.48, 75.75, 70.85,57.44, 56.43, 54.08, 48.63, 46.35, 43.61, 37.36, 31.55, 20.45, 16.82,13.94; IR (neat film) 2961 (m), 1838 (s), 1743 (s), 1655 (s), 1487 (s),1376 (w), 1037 (s), 731 (s) cm⁻¹; LRMS (ESI) (calcd for C₂₅H₃₀NO₇ (M⁺+H)455.19 found 455.96; [α]_(D)=−120° (c 1.13, CDCl₃).

Bis(de-methyl)-deoxyharringtonine I-4. To a solution of β-lactone I-1(9.5 mg, 0.021 mmol, 1.0 equiv) in MeOH (210 μL) was added a freshlyprepared solution of 0.5M NaOMe in MeOH (4.2 μL, 0.0021 mmol, 0.1equiv). After 15 min the solution was quenched with sat'd NH₄Cl solution(10 mL) and extracted with CH₂Cl₂ (3×10 mL). The combined organic phaseswere dried over MgSO₄ and concentrated by rotary evaporation to yieldI-4 (9.5 mg, 93%) as a colorless oil without need for furtherpurification. R_(f)=0.40 (2% TEA in 9:1 toluene:EtOAc on platespretreated with 5% TEA in pentane); ¹H NMR (500 MHz, CDCl₃) δ 6.62 (s,1H, ArH), 6.54 (s, 1H, ArH), 5.98 (d, 1H, J=9.8 Hz, ArCHCH), 5.87 (d,2H, J=5.7 Hz, OCH₂O), 5.04 (s, 1H, vinyl H), 3.77 (d, 1H, J=9.8 Hz,ArCHCH), 3.68 (s, 3H, OCH₃), 3.57 (s, 3H, OCH₃), 3.47 (s, 1H, OH),3.17-3.07 (m, 2H, CH₂), 2.99-2.90 (m, 1H, CH₂), 2.63-2.56 (m, 2H, CH₂),2.38 (dd, 1H, J=14.1, 6.8 Hz, CH₂), 2.29 (d, 1H, J=16.5 Hz, C(O)CH₂),2.07-2.00 (m, 1H, CH₂), 2.00 (d, 1H, J=16.6, C(O)CH₂), 1.93-1.87 (m, 1H,CH₂), 1.80-1.71 (m, 2H, CH₂), 1.44-1.27 (m, 3H, CH₂), 1.14-1.05 (m, 1H,CH₂), 0.83 (t, 3H, J=7.2 Hz, CH₂CH₃); ¹³C NMR (100 MHz, CDCl₃) δ 174.15,170.63, 157.89, 146.83, 145.96, 133.51, 128.44, 112.81, 109.83, 100.95,100.21, 74.96, 74.85, 70.76, 57.33, 56.06, 54.10, 51.62, 48.77, 43.58,42.75, 41.16, 31.52, 20.45, 16.29, 14.22; IR (neat film) 3525 (w), 2958(m), 1747 (s), 1654 (m), 1503 (m), 1487 (s), 1225 (s), 1037 (s), 731 (w)cm⁻¹; LRMS (ESI) calcd for C₂₆H₃₄NO₈ (M⁺+H) 488.22 found 487.84;[α]_(D)=−124° (c 0.95, CDCl₃).

General Procedures: Cytotoxicity Evaluations

Cell Line Panel.

The cell line panel used in this study included HL-60 (a human acutepromyelocytic leukemia cell line), HL-60/RV+ (a P-glycoproteinover-expressing multidrug resistant HL-60 variant which was selected bycontinuous exposure to the vinca alkaloid vincristine), JURKAT (a humanT cell leukemia cell line), ALL3 (acute lymphoblastic leukemia recentlyisolated from a patient treated at Memorial Sloan-Kettering CancerCenter (MSKCC) and characterized as Philadelphia chromosome positive(Ph⁺); provided by Dr. Mark Frattini, MSKCC), NCEB1 (a Mantle celllymphoma cell line), JEKO (a human B cell lymphoma), MOLT-3 (a humanacute lymphoblastic T-cell line), SKNLP (a human neuroblastoma cellline), Y79 (a human retinoblastoma cell line isolated by explant cultureof a primary tumor from the right eye immediately after enucleation),PC9, H1650, H1975, H2030, H3255 (all human non-small cell lung cancercell lines derived from patients with pulmonary adenocarcinoma), TC71 (asarcoma cell line obtained from tumor tissue of recurrent Ewing'ssarcoma), HTB-15 (a human glioblastoma cell line), A431 (a humanepithelial carcinoma cell line), HeLa (a human cervical adenocarcinomacell line), and WD0082 (a human liposarcoma cell line isolated from awell-differentiated liposarcoma patient; provided by Dr. S. Singer,MSKCC). All of the cell lines were grown at 37° C. in a 5% CO₂ incubatorusing standard culture medium, which consisted of RPMI 1640 supplementedwith 10% bovine calf serum, 2 mM glutamine, 100 IU/ml of penicillin, and100 μg/ml of streptomycin or as recommended by the ATCC.

Proliferation Assay. The assay used for the cytotoxicity evaluation isbased on the dye resazurin and commercially sold as Alamar Blue (SerotecLtd, USA). Cells were seeded at densities ranging from 250 to 20,000cells in 45 μL of medium to compound containing plates and incubated for72 hours at 37° C. in a 5% CO₂ incubator; at which time 5 μL of theAlamar Blue reagent was added and the cells were further incubated foranother 24 hours, before the fluorescence intensity was read on theAmersham LEADseeker™ Multimodality Imaging System (GE, USA). The assayswere performed on a fully automated linear track robotic platform (CRSF3 Robot System, Thermo Electron, Canada) using several integratedperipherals for plate handling, liquid dispensing, and fluorescencedetection. Screening data files from the imaging system were loaded intothe HTS Core Screening Data Management System, a custom built suite ofmodules for compound registration, plating, data management, and poweredby ChemAxon Cheminformatic tools (ChemAxon, Hungary). Data analysis andcurve fitting was performed on all the compounds tested, and the datasummary exported as SD files for further analysis and reporting.

Dose Response Studies. In each assay, the signal inhibition induced bythe compounds was expressed as a percentage compared to high and lowcontrols located on the same plate, as defined as % Inhibition=(highcontrol average−read value)/(high control average−low controlaverage)×100. The dose response was assessed in duplicate and using 12point doubling dilutions with either 1, 10 or 100 μM compoundconcentration as the upper limit. The dose response curve for each setof data was fitted seperately, and the two IC₅₀ values obtained wereaveraged.

What is claimed is:
 1. A compound of formula I:

or a pharmaceutically acceptable salt thereof; wherein: each

independently designates a single or double bond; R¹ is hydrogen,optionally substituted C₁₋₆ aliphatic, —(CH₂)_(n)CO₂R⁸,—(CH₂)_(n)CON(R⁸)₂, —(CH₂)_(n)COSR⁸, or taken together with R² to forman optionally substituted, saturated or unsaturated 3-7-membered ringhaving 0-2 heteroatoms independently selected from nitrogen, oxygen, orsulfur; and each R⁸ is independently hydrogen, an optionally substitutedgroup selected from cephalotaxine, C₁₋₆ aliphatic, 6-10-membered aryl,or C₁₋₆ heteroaliphatic having 1-2 heteroatoms independently selectedfrom nitrogen, oxygen, or sulfur; n is an integer from 0-4; R² ishydrogen, —NR₂, —OR, or an optionally substituted group selected fromacyl, C₁₋₆ aliphatic, or C₁₋₆ heteroaliphatic having 1-2 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; R³ is -T-R^(z),wherein: T is a covalent bond or a bivalent C₁₋₁₂ saturated orunsaturated, straight or branched, hydrocarbon chain, wherein one or twomethylene units of T are optionally and independently replaced by —O—,—S—, —N(R)—, —C(O)—, —C(O)O—, —OC(O)—, —N(R)C(O)—, —C(O)N(R)—, —S(O),—S(O)₂—, —N(R)SO₂—, or —SO₂N(R)—; and R^(z) is hydrogen, halogen, amonosaccharide, a disaccharide, —OR, —SR, —NR₂, —N₃, or an optionallysubstituted group selected from acyl, arylalkyl, heteroarylalkyl, C₁₋₆aliphatic, 6-10-membered aryl, 5-10-membered heteroaryl having 1-4heteroatoms independently selected from nitrogen, oxygen, or sulfur,4-7-membered heterocyclyl having 1-2 heteroatoms independently selectedfrom nitrogen, oxygen or sulfur; or a hydrogen radical on R^(z) isreplaced with a substituent of the formula:

wherein each occurrence of R¹, R², R⁴, R⁵, R⁶, R⁷, T, and R^(z) may bethe same or different; R⁴ is hydrogen, —OR, or ═O; R⁵ and R⁶ are eachindependently selected from hydrogen, C₁₋₆ aliphatic, —SO₂R, —CO₂R; orR⁵ and R⁶ are taken together with their intervening atoms to form anoptionally substituted 5-7-membered ring having 0-2 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; R⁷ is hydrogen,—OR, —OCO₂R, —OCOR, —OCOSR, or —OCONR₂; and each R is independentlyhydrogen, an optionally substituted group selected from acyl, arylalkyl,C₁₋₆ aliphatic, or C₁₋₆ heteroaliphatic having 1-2 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; or two R on thesame nitrogen atom are taken with the nitrogen to form a 4-7-memberedheterocyclic ring having 1-2 heteroatoms independently selected fromnitrogen, oxygen, or sulfur; with the proviso that at least one of R⁵,R⁶, or R⁷is not hydrygen.
 2. The compound of claim 1, wherein neither R⁵nor R⁶ is hydrogen.
 3. The compound of claim 1, wherein R¹ is takentogether with R² to form an optionally substituted, saturated orunsaturated 3-7-membered ring having 0-2 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur.
 4. The compound of claim 1wherein R¹ is —(CH₂)_(n)CO₂R⁸.
 5. The compound of claim 4, wherein n is1, and R⁸ is methyl.
 6. The compound of claim 4, wherein R⁸ is —CH₂F. 7.The compound of claim 3, wherein R¹ and R² are taken together to form


8. The compound of claim 1, wherein R² is —OR.
 9. The compound of claim8, wherein R is H.
 10. The compound of claim 1, wherein R³ is -T-R^(z),wherein: T is a covalent bond or a bivalent C₁₋₁₂ saturated orunsaturated, straight or branched, hydrocarbon chain, wherein one or twomethylene units of T are optionally and independently replaced by —O—,—S—, or —N(R)—; and R^(z) is hydrogen, halogen, a monosaccharide, adisaccharide, —OR, —SR, —NR₂, —N₃, or an optionally substituted groupselected from acyl, arylalkyl, heteroarylalkyl, C₁₋₆ aliphatic,6-10-membered aryl, 5-10-membered heteroaryl having 1-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur, 4-7-memberedheterocyclyl having 1-2 heteroatoms independently selected fromnitrogen, oxygen or sulfur.
 11. The compound of claim 10, wherein T isselected from a covalent bond,


12. The compound of claim 1, wherein R^(z) is hydrogen, hydroxy,halogen, methyl, ethyl, phenyl, benzyl, —N₃, a monosaccharide, adisaccharide,


13. The compound of claim 1, wherein both R⁵ and R⁶ are hydrogen. 14.The compound of claim 1, wherein R⁷ is hydrogen or —OCO₂R.
 15. Thecompound selected from the group consisting of:


16. A pharmaceutical composition comprising a compound of claim 1 orclaim 15 and a pharmaceutically acceptable excipient.
 17. A method fortreating cancer in a subject suffering therefrom comprisingadministering to the subject a therapeutically effective amount of acompound of claim 1 or claim
 15. 18. A compound of formula II:

or a pharmaceutically acceptable salt thereof, wherein: each

independently designates a single or double bond; R¹ is hydrogen,optionally substituted C₁₋₆ aliphatic, —(CH₂)_(n)CO₂R⁸,—(CH₂)_(n)CON(R⁸)₂, —(CH₂)_(n)COSR⁸, or taken together with R² to forman optionally substituted, saturated or unsaturated 3-7-membered ringhaving 0-2 heteroatoms independently selected from nitrogen, oxygen, orsulfur; and each R⁸ is independently hydrogen, an optionally substitutedgroup selected from cephalotaxine, C₁₋₆ aliphatic, 6-10-membered aryl,or C₁₋₆ heteroaliphatic having 1-2 heteroatoms independently selectedfrom nitrogen, oxygen, or sulfur; n is an integer from 0-4; R² ishydrogen, —NR₂, —OR, or an optionally substituted group selected fromacyl, C₁₋₆ aliphatic, or C₁₋₆ heteroaliphatic having 1-2 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; R³ is -T-R^(z),wherein: T is a covalent bond or a bivalent C₁₋₁₂ saturated orunsaturated, straight or branched, hydrocarbon chain, wherein one or twomethylene units of T are optionally and independently replaced by —O—,—S—, —N(R)—, —C(O)—, —C(O)O—, —OC(O)—, —N(R)C(O)—, —C(O)N(R)—, —S(O),—S(O)₂—, —N(R)SO₂—, or —SO₂N(R)—; and R^(z) is hydrogen, halogen, amonosaccharide, a disaccharide, —OR, —SR, —NR₂, —N₃, or an optionallysubstituted group selected from acyl, arylalkyl, heteroarylalkyl, C₁₋₆aliphatic, 6-10 -membered aryl, 5-10 -membered heteroaryl having 1-4heteroatoms independently selected from nitrogen, oxygen, or sulfur,4-7-membered heterocyclyl having 1-2 heteroatoms independently selectedfrom nitrogen, oxygen or sulfur; or a hydrogen radical on R^(z) isreplaced with a substituent of the formula:

wherein each occurrence of R¹, R², R⁵, R⁶, R⁷, T, and R^(z) may be thesame or different; R⁵ and R⁶ are each independently selected fromhydrogen, C₁₋₆ aliphatic, —SO₂R, —CO₂R; or R⁵ and R⁶ are taken togetherwith their intervening atoms to form an optionally substituted5-7-membered ring having 0-2 heteroatoms independently selected fromnitrogen, oxygen, or sulfur; R⁷ is hydrogen, —OR, —OCO₂R, —OCOR, —OCOSR,or —OCONR₂; and each R is independently hydrogen, an optionallysubstituted group selected from acyl, arylalkyl, C₁₋₆ aliphatic, or C₁₋₆heteroaliphatic having 1-2 heteroatoms independently selected fromnitrogen, oxygen, or sulfur; or: two R on the same nitrogen atom aretaken with the nitrogen to form a 4-7-membered heterocyclic ring having1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur.19. The method of claim 17, wherein the cancer is a hematologicalmalignancy.
 20. The method of claim 19, wherein the cancer is acutelymphoblastic leukemia (ALL), acute myelogenous leukemia (AML), chronicmyelogenous leukemia (CML), chronic lymphocytic leukemia (CLL),Hodgkin's lymphoma, T-cell lymphoma (TCL), B-cell lymphoma, or multiplemyeloma.
 21. The method of claim 17, wherein the cancer is a multidrugresistant cancer.
 22. A method of claim 17, further comprisingadministering to the subject a therapeutically effective amount of asecond chemotherapeutic agent.